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One embodiment describes a switching device system, which includes a
first single pole switching device that selectively connects and
disconnects a first phase of electric power to a first winding of a three
phase motor; a second single switching device that selectively connects
and disconnects a second phase of electric power to a second winding of
the three phase motor; in which the first and second single pole
switching devices control temperature of the motor by, at a first time,
connecting the first phase and the second phase electric power to the
motor.

1. A switching device system comprising: a switching device comprising
contactor pads, wherein the switching device is configured to connect
electric power to a load when the contactor pads are electrically
connected and to disconnect electric power from the load when the
contactor pads are electrically disconnected; and a control circuitry
configured to: determine whether desirable to clean the contactor pads
when disconnecting electric power from the load; when cleaning is not
desired, instruct the switching device to disconnect the contactor pads
at a first time based on a current zero-crossing; and when cleaning is
desired, instruct the switching device to disconnect the contactor pads
at a second time such that an arc is produced to clean the contactor
pads.

2. The switching device system of claim 1, wherein the control circuitry
is configured to instruct the switching device to disconnect the
contactor pads based on the current zero-crossing by instructing the
switching device to disconnect the contactor pads at or slightly before
the current zero-crossing.

3. The switching device of claim 1, wherein the control circuitry is
configured to determine the second time based at least in part on desired
magnitude of the arc.

4. The switching device of claim 3, wherein the second time is farther
from current zero-crossings to increase magnitude of the arc and closer
to the current zero-crossings to decrease magnitude of the arc.

5. The switching device of claim 1, wherein the control circuitry is
configured to instruct the switching device to disconnect the contactor
pads at the second time such that the arc burns off oxidation on the
contactor pads.

6. The switching device claim 1, wherein the control circuitry is
configured to determine the second time such that the contactor pads
alternate as anode and cathode in each arc.

7. The switching device of claim 1, wherein the switching device
comprises a single pole, single current carrying path switching device; a
single pole, multi current carrying path switching device; or a multi
pole, multi current carrying path switching device.

8. A switching device system comprising: a switching device comprising
contactor pads, wherein the switching device is configured to connect
electric power to a load when the contactor pads are electrically
connected and to disconnect electric power from the load when the
contactor pads are electrically disconnected; and a control circuitry
configured to control switching in at least some cycles of the switching
device to clean the contactor pads by producing an arc between the
contactor pads, and to control the switching device in other times based
upon a point-on-wave switching scheme to avoid arcs between the contactor
pads.

9. The switching device of claim 8, wherein the point-on-wave switching
scheme is based upon a zero-crossing of a power waveform.

10. The switching device of claim 8, wherein the control circuitry is
configured to instruct the switching device to disconnect the contactor
pads based on a current zero-crossing by instructing the switching device
to disconnect the contactor pads at or slightly before the current
zero-crossing.

11. The switching device of claim 8, wherein the control circuitry is
configured to determine a desired switching time based at least in part
on desired magnitude of the arc.

12. The switching device of claim 11, wherein the switching time is
farther from a current zero-crossings to increase magnitude of the arc
and closer to the current zero-crossings to decrease magnitude of the
arc.

13. The switching device of claim 8, wherein the control circuitry is
configured to instruct the switching device to disconnect the contactor
pads at a switching time such that the arc burns off buildup on the
contactor pads.

14. The switching device claim 8, wherein the control circuitry is
configured to determine a switching time such that the contactor pads
alternate as anode and cathode in each arc.

15. The switching device of claim 8, wherein the switching device
comprises a single pole, single current carrying path switching device.

16. A method of cleaning contactor pads in a switching device,
comprising: determining, using control circuitry, that desirable to break
the switching device to disconnect electric power from a load;
determining, using the control circuitry, whether desirable to clean the
contactor pads when disconnecting electric power; instructing, using the
control circuitry, the switching device to break such that the contactor
pads disconnect at a first time based at least in part on a
current-zero-crossing; and instructing, using the control circuitry, the
switching device to break such that the contactor pads disconnect at a
second time different from the first time to create an arc between the
contactor pads.

17. The method of claim 16, wherein instructing the switching device to
break at the first time comprises instruct the switching to break at the
first time such that the contactor pads disconnect at or slightly before
the current zero-crossing.

18. The method of claim 16, comprising determine the second time based at
least in part on duration the switching device is closed, duration the
switching device has been in operation, or both.

18. The method of claim 16, comprising determining the second time based
at least in part on desired magnitude of the arc.

20. The method of claim 16, wherein the second time is closer to current
zero-crossings when desired magnitude is greater and farther from the
current zero-crossings when desired magnitude is lower.

[0002] The present disclosure relates generally to switching devices, and
more particularly to operation and configuration of the switching
devices.

[0003] Switching devices are generally used throughout industrial,
commercial, material handling, process and manufacturing settings, to
mention only a few. As used herein, "switching device" is generally
intended to describe any electromechanical switching device, such as
mechanical switching devices (e.g., a contactor, a relay, air break
devices, and controlled atmosphere devices) or solid state devices (e.g.,
a silicon-controlled rectifier (SCR)). More specifically, switching
devices generally open to disconnect electric power from a load and close
to connect electric power to the load. For example, switching devices may
connect and disconnect three-phase electric power to an electric motor.
As the switching devices open or close, electric power may be discharged
as an electric arc and/or cause current oscillations to be supplied to
the load, which may result in torque oscillations. To facilitate reducing
likelihood and/or magnitude of such effects, the switching devices may be
opened and/or closed at specific points on the electric power waveform.
Such carefully timed switching is sometimes referred to as "point on
wave" or "POW" switching. However, the opening and closing of the
switching devices are generally non-instantaneous. For example, there may
be a slight delay between when the make instruction is given and when the
switching device actually makes (i.e., closes). Similarly, there may be a
slight delay between when break instruction is given and when the
switching device actually breaks (i.e., opens).

[0004] Accordingly, to facilitate making or breaking at a specific point
on the electric power waveform, it would be beneficial to determine the
delay. More specifically, this may include determining when the switching
device makes or breaks.

[0005] Additionally, since the switching devices may make to supply
electric power to a load, it would be beneficial to determine if there
are any faults, such as a phase-to-ground short or a phase-to-phase
short, before fully connecting electric power to the load. For example,
testing for faults before fully connecting electric power may enable the
faults to be detected while minimizing the peak current and/or let
through energy resulting from the fault condition.

[0006] Furthermore, switching devices may be utilized to provide electric
power to electric motors. For example, in some applications, the
switching devices may be included in a wye-delta starter or some other
motor controlling device. As used herein, a "wye-delta starter" is
intended to describe a device that controls operation (e.g., speed,
torque, and/or power consumption) of an electric motor by connecting
winding in the electric motor in a wye configuration, a delta
configuration, or a mixed wye-delta configuration. In fact, in addition
to controlling starting of the electric motor, the wye-delta starter may
control operation and even stopping of the electric motor.

More specifically, the electric motor may be started by connecting the
windings in the motor in a wye configuration to reduce voltage supplied
to the windings, which may also reduce the torque produced by the motor.
Once started, the windings in the motor may be connected in a delta
configuration to increase the voltage supplied to the windings, which may
increase the torque produced by the motor. However, as described above,
opening and closing the switching devices to connect the electric motor
in the wye configuration and to transition from the wye configuration to
the delta configuration may discharge electric power (e.g., arcing)
and/or cause current oscillations to be supplied to the motor. In some
embodiments, reducing the likelihood and magnitude of electric arcing
and/or current oscillations may increase the lifespan of the switching
devices.

[0007] Accordingly, it would be beneficial to reduce the likelihood and
magnitude of electric arcing and/or currently oscillations produced when
making or breaking a switching device. More specifically, this may
include opening and/or closing switching devices in the wye-delta starter
at specific points on the electric power waveform.

[0008] Moreover, wye-delta starters generally supply electric power to
electric motors to run the motors in wye or delta configuration. More
specifically, when the motor is run in a wye configuration, the electric
motor may use less electric power and produce a first (e.g., lower)
torque level, and when the motor is run in a delta configuration, the
electric motor may use more electric power and produce a second (e.g.,
higher) torque level. In other words, running the electric motor with a
wye-delta starter enables two operating modes (e.g., less power
consumption lower torque and more power consumption higher torque).
However, there may be instances when it is desirable to operate the motor
somewhere between the two operating modes. For example, it may be
desirable to produce more torque than produced when operating in the wye
configuration, but consume less electric power than consumed when
operating in the delta configuration. Accordingly, it would be beneficial
to increase the operational flexibility of a wye-delta starter.

[0009] After the electric motor is spinning, electric power may be
disconnected from the motor for various reasons, such as a brownout or a
lightning strike. More specifically, switching devices (e.g., contactors)
may open to disconnect electric power. Once power is disconnected, the
momentum of the rotation may keep the motor spinning, but friction (e.g.,
air resistance) may begin to slow the motor. As such, the frequency of
the motor gradually decreases. Subsequently, the electric motor may be
restarted by re-closing the switching devices to connect electric power
to the motor. In some embodiments, such as reliability sensitive
implementation, it may be desirable to restart the electric motor as soon
as possible, for example, while the electric motor is still spinning.
However, since the frequency of the motor is changing, the phase
relationship of the motor relative to the electric power source is also
changing, thereby creating a "beat" condition. Therefore, the motor may
be out of phase from the source when re-closing the switching devices to
reconnect electric power to the motor, which may result in current
oscillations and/or torque oscillations. In some embodiments, minimizing
the likelihood and magnitude of current oscillations and/or torque
oscillations may increase the lifespan of the electric motor and/or a
connected load. In some embodiments, minimizing peaks in the current may
reduces nuisance tripping of protective circuitry (e.g., circuit breaker
or fuses) and, thus, enable the protective circuitry to be sized more
advantageously.

[0010] Accordingly, it would be beneficial to minimize the magnitude and
likelihood of current oscillations and/or torque oscillations produced
when the electric motor is restarted. More specifically, this may include
restarting the electric motor when the phase of the electric power and
the electric motor are substantially in phase, when the phase of the
electric power is leading the phase of the electric motor, or at some
other desired condition.

[0011] As will be described in more detail below, many of the benefits
described may be enabled by increasing the amount of control over the
electric power supplied to a load. For example, independently controlling
each phase of three-phase power may enable detection of faults (e.g., a
phase-to-ground short or a phase-to-phase short) while minimizing the
duration, the peak current, and/or the let through energy of the faulty
condition. Accordingly, it would be beneficial to utilize a switching
device capable of increasing control over electric power supplied to the
load, for example, by enabling each phase of electric power to be
independently controlled.

[0012] Additionally, since switching device may be utilized in various
implementations, such as a wye-delta starter, a reverser, a motor drive
bypass, and so forth, it would be beneficial to utilize a switching
device that can be modularly configured for various implementations, for
example, to minimize footprint and/or interconnections (e.g., cabling) of
the switching devices. More generally, modular arrangements, such as
single-phase switching modules that can be incorporated alone or as a
group, may enable a highly flexible modular design and manufacturing
platform, which allows for assemblies of devices for many different needs
and markets.

[0013] Moreover, while many of the foregoing improvements may be used
together, they may also be used separately with significant potential for
improvement in the field of switching and power systems. For example,
single-phase switching devices may be used in POW (e.g., timed)
application and/or conventional (e.g., non-timed) applications.
Additionally, a motor control device (e.g., a wye-delta starter) may also
be used in POW (e.g., timed) application and/or conventional (e.g.,
non-timed) applications. The present disclosure relates to various
different technical improvements in the field, which may be used in
various combinations to provide advances in the art.

DRAWINGS

[0014] These and other features, aspects, and advantages of the present
disclosure will become better understood when the following detailed
description is read with reference to the accompanying drawings in which
like characters represent like parts throughout the drawings, wherein:

[0015] FIG. 1 is a diagrammatical representation of a set of switching
devices to provide power to an electrical load, in accordance with an
embodiment;

[0016] FIG. 2 is a similar diagrammatical representation of a set of
switching devices to provide power to an electrical motor, in accordance
with an embodiment;

[0017] FIG. 3 is a similar diagrammatical representation of a set of
switching devices to provide power to an electrical motor, in accordance
with an embodiment;

[0018] FIGS. 4A-4D is a similar diagrammatical representation of a set of
switching devices to provide power to a specific application, in this
case a chiller motor, in accordance with an embodiment;

[0019] FIGS. 5A-5C is a diagrammatical representation of three-phase POW
switching to provide power to a load, in accordance with an embodiment;

[0020] FIG. 6 is a diagrammatical representation of three-phase POW
switching to disconnect power from a load, in accordance with an
embodiment;

[0021] FIG. 7 is a perspective view of a single-pole, single
current-carrying path switching device, in accordance with an embodiment;

[0022] FIG. 8 is a perspective exploded view of the device of FIG. 7, in
accordance with an embodiment;

[0023] FIG. 9 is a top perspective view of certain of the internal
components and assemblies of the single-pole, single current-carrying
path switching device, in accordance with an embodiment;

[0024] FIG. 10 is a bottom perspective view of the internal components and
assemblies of the device, in accordance with an embodiment;

[0025] FIG. 11 is a side view of the internal components and assemblies of
the device, in accordance with an embodiment;

[0026] FIG. 12 is a partially sectioned side view of the internal
components and assemblies of the device in an open position, in
accordance with an embodiment;

[0027] FIG. 13 is a top perspective view of a movable contact structure
for the device, in accordance with an embodiment;

[0028] FIG. 14 is a partially sectioned side view of the internal
components and assemblies of the device in an open position, in
accordance with an embodiment;

[0029] FIG. 15 is a detailed view of one aspect of the device structure,
in accordance with an embodiment;

[0030] FIG. 16 is a detailed view of a further aspect of the device
structure, in accordance with an embodiment;

[0031] FIG. 17A is a detailed view of an optional armature arrangement of
the device structure, in accordance with an embodiment;

[0032] FIG. 17B is a diagrammatical representation of a similar device
with a dedicated sensing winding or coil, in accordance with an
embodiment;

[0033] FIG. 18 is a perspective view of a splitter plate for the device,
in accordance with an embodiment;

[0034] FIG. 19 is a perspective view of an internal construction of the
device housing to help channel and cool gases, in accordance with an
embodiment;

[0035] FIG. 20 is a partially sectional view representing the channeling
of gases during operation of the device, in accordance with an
embodiment;

[0036] FIG. 21 is a top view of a pair of single-pole switching devices
joined by a mechanical interlock, in accordance with an embodiment;

[0037] FIG. 22 is a perspective view of a system assembled with multiple
single-pole switching devices with electrical interconnects, in
accordance with an embodiment;

[0038] FIG. 23 is a perspective view of a mechanical interlock that may be
used in the assemblies, in accordance with an embodiment;

[0039] FIG. 24 is an exploded view of the mechanical interlock, in
accordance with an embodiment;

[0040] FIG. 25 is a circuit diagram of an operating coil driver circuitry
for use with the single-pole switching device, in accordance with an
embodiment;

[0041] FIGS. 26A and 26B are a diagrammatical representations of coil
current waveforms for closing of the device, in accordance with an
embodiment;

[0042] FIG. 27 is a voltage waveform illustrating timing considerations
for closing the device, in accordance with an embodiment;

[0043] FIG. 28 is a block diagram of logic for timing closing of the
device, in accordance with an embodiment;

[0044] FIG. 29 is a PWM waveform for determining closing the device, in
accordance with an embodiment;

[0045] FIG. 30 is a block diagram of logic for closing the device, in
accordance with an embodiment;

[0046] FIG. 31 is a diagrammatical representations of coil control
waveforms for opening of the device, in accordance with an embodiment;

[0047] FIG. 32 is a voltage or current waveform illustrating timing
considerations for opening the device, in accordance with an embodiment;

[0048] FIG. 33 is a block diagram of logic for timing opening of the
device, in accordance with an embodiment;

[0049] FIGS. 34A and 34B are a PWM waveform for determining opening the
device, in accordance with an embodiment;

[0050] FIG. 35 is a block diagram of logic for determining opening the
device, in accordance with an embodiment;

[0051] FIG. 36 is a diagrammatical representation of an alternate
embodiment of an operator coil driving circuit, in accordance with an
embodiment;

[0052] FIG. 37 is a diagrammatical representation of a power scenario
during switching of the device, in accordance with an embodiment;

[0053] FIG. 38 is a coil operation to temperature relationship, in
accordance with an embodiment;

[0054] FIG. 39 is a block diagram of logic for temperature detection
(e.g., relative) and adaptation, in accordance with an embodiment;

[0055] FIG. 40 is a similar block diagram of logic for monitoring
temperature during operation, in accordance with an embodiment;

[0056] FIGS. 41A-41D are block diagrams of logic for determining wellness
of a component, load and/or system based upon monitoring of operator coil
parameters, in accordance with an embodiment;

[0057] FIGS. 42A-42D is a block diagram of logic for the sequential
switching of single pole switching devices, in accordance with an
embodiment;

[0058] FIGS. 43A-43H is a set of equivalent circuit diagrams illustrating
phase sequential wye-delta switching utilizing single-pole switching
devices for controlling a three-phase motor, in accordance with an
embodiment;

[0059] FIG. 44A is a block diagram of logic for the phase sequential
wye-delta switching, in accordance with an embodiment;

[0060] FIG. 44B is plot of current in windings of an electric motor during
phase sequential wye-delta switching, in accordance with an embodiment;

[0061] FIGS. 45A-45C is a set of current and voltage waveforms for the
phase sequential wye-delta switching, in accordance with an embodiment;

[0062] FIG. 46 is a block diagram of logic for switching between wye and
delta configurations during operation of a motor, in accordance with an
embodiment;

[0064] FIG. 48 is a block diagram of logic for wye-delta motor starting
over a series of starts, in accordance with an embodiment;

[0065] FIGS. 49A-49D are circuit diagrams for 8 and 9 pole wye-delta
switching arrangements, in accordance with an embodiment;

[0066] FIGS. 50A-50F is a set of equivalent circuit diagrams illustrating
phase sequential wye-delta switching referenced to known, predicted, or
estimated drive torques applied to a three-phase motor, in accordance
with an embodiment;

[0067] FIG. 50G is a plot of torque produced by an electric motor during
phase sequential wye-delta switching, in accordance with an embodiment;

[0068] FIGS. 51A and 51B is a set of block diagrams of logic for the
torque-referenced and power-referenced phase sequential wye-delta
switching, in accordance with an embodiment;

[0069] FIG. 52 is a voltage or current waveform illustrating timing
considerations for POW switching based upon an operator-received
initiation command, in accordance with an embodiment;

[0070] FIG. 53 is a block diagram of logic for operator-initiated POW
switching, such as for starting a polyphase motor, in accordance with an
embodiment;

[0071] FIG. 54 is a waveform for a motor drive signal and a motor back EMF
signal illustrating timing of the signals during deceleration (or
acceleration) of the motor for re-applying drive signals, in accordance
with an embodiment;

[0072] FIG. 55 is a block diagram of logic for synchronously reclosing a
switching circuit for re-applying drive signals to a motor, in accordance
with an embodiment;

[0073] FIGS. 56A and 56B is a diagrammatical representation of circuitry
for detecting motor conditions utilizing single-pole switching devices
and a corresponding timing diagram, respectively, in accordance with an
embodiment;

[0074] FIG. 57 is a block diagram of logic for detecting motor conditions,
in accordance with an embodiment;

[0075] FIGS. 58A and 58B is a diagrammatical representation of alternative
circuitry for detecting motor conditions utilizing multiple single-pole
switching devices and a corresponding timing diagram, respectively, in
accordance with an embodiment;

[0076] FIG. 59 is a graphical representation of timing for the motor
condition detection, in accordance with an embodiment;

[0077] FIG. 60 is a diagrammatical representation of a circuit for a 5
pole wye-delta starter constructed of multiple single-pole switching
devices interconnected with one another, in accordance with an
embodiment;

[0078] FIG. 61 is a top view of an assembly of single-pole switching
devices to create the circuit of FIG. 60, in accordance with an
embodiment;

[0079] FIG. 62 is a diagrammatical representation of a circuit for a 6
pole wye-delta starter constructed of multiple single-pole switching
devices interconnected with one another, in accordance with an
embodiment;

[0080] FIG. 63 is a top view of an assembly of single-pole switching
devices to create the circuit of FIG. 62, in accordance with an
embodiment;

[0081] FIG. 64 is a diagrammatical representation of a circuit for an 8
pole wye-delta starter constructed of multiple single-pole switching
devices interconnected with one another, in accordance with an
embodiment;

[0082] FIG. 65 is a top view of an assembly of single-pole switching
devices to create the circuit of FIG. 64, in accordance with an
embodiment;

[0083] FIG. 66 is a diagrammatical representation of a circuit for a 9
pole wye-delta starter constructed of multiple single-pole switching
devices interconnected with one another, in accordance with an
embodiment;

[0084] FIG. 67 is a top view of an assembly of single-pole switching
devices to create the circuit of FIG. 66, in accordance with an
embodiment;

[0085] FIG. 68 is a diagrammatical representation of an circuit for an
alternative 9 pole wye-delta starter constructed of multiple single-pole
switching devices interconnected with one another, in accordance with an
embodiment;

[0086] FIG. 69 is a top view of an assembly of single-pole switching
devices to create the circuit of FIG. 68, in accordance with an
embodiment;

[0087] FIG. 70 is a diagrammatical representation of a circuit for a 5
pole reverser constructed of multiple single-pole switching devices
interconnected with one another, in accordance with an embodiment;

[0088] FIG. 71 is a top view of an assembly of single-pole switching
devices to create the circuit of FIG. 70, in accordance with an
embodiment;

[0089] FIG. 72 is a diagrammatical representation of a circuit for a motor
drive bypass constructed of multiple single-pole switching devices
interconnected with one another, in accordance with an embodiment;

[0090] FIG. 73 is a top view of an assembly of single-pole switching
devices to create the circuit of FIG. 72, in accordance with an
embodiment;

[0091] FIG. 74 is a diagrammatical representation of a three single-pole
switching device configuration used in various control schemes, in
accordance with an embodiment;

[0092] FIG. 75 is a diagrammatical representation of a four single-pole
switching device configuration used in various control schemes, in
accordance with an embodiment;

[0093] FIG. 76 is a perspective view of two single-pole switching devices
connected via a bus bar, in accordance with an embodiment;

[0094] FIG. 77 is a perspective view of two single-pole switching devices
with varying height power terminals connected via a single connector pin,
in accordance with an embodiment;

[0095] FIG. 78 is a perspective view of two single-pole switching devices
with mating power terminals connected via a single connector pin, in
accordance with an embodiment;

[0096] FIG. 79 is a top view of three single-pole switching devices with
varying height power terminals connected via a single connector pin, in
accordance with an embodiment;

[0097] FIG. 80 is a top view of three single-pole switching devices
connected via a "T" bus bar, in accordance with an embodiment;

[0098] FIG. 81 is a block diagram of logic for controlling temperature of
an electric motor, in accordance with an embodiment; and

[0099] FIG. 82 is a block diagram of logic for cleaning contactor pads of
a switching device, in accordance with an embodiment.

DETAILED DESCRIPTION

[0100] One or more specific embodiments of the present disclosure will be
described below. In an effort to provide a concise description of these
embodiments, all features of an actual implementation may not be
described in the specification. It should be appreciated that in the
development of any such actual implementation, as in any engineering or
design project, numerous implementation-specific decisions must be made
to achieve the developers' specific goals, such as compliance with
system-related and business-related constraints, which may vary from one
implementation to another. Moreover, it should be appreciated that such a
development effort might be complex and time consuming, but would
nevertheless be a routine undertaking of design, fabrication, and
manufacture for those of ordinary skill having the benefit of this
disclosure.

[0101] When introducing elements of various embodiments of the present
disclosure, the articles "a," "an," "the," and "said" are intended to
mean that there are one or more of the elements. The terms "comprising,"
"including," and "having" are intended to be inclusive and mean that
there may be additional elements other than the listed elements.

[0102] As described above, switching devices are used in various
implementations, such as industrial, commercial, material handling,
manufacturing, power conversion, and/or power distribution, to connect
and/or disconnect electric power from a load. To help illustrate, FIG. 1
depicts a system 10 that includes a power source 12, a load 14, and
switchgear 16, which includes one or more switching devices. In the
depicted embodiment, the switchgear 16 may selectively connect and/or
disconnect three-phase electric power output by the power source 12 to
the load 14, which may be an electric motor or any other powered device.
In this manner, electrical power flows from the power source 12 to the
load 14. For example, switching devices in the switchgear 16 may close to
connect electric power to the load 14. On the other hand, the switching
devices in the switchgear 16 may open to disconnect electric power from
the load 14. In some embodiments, the power source 12 may be an
electrical grid.

[0103] It should be noted that the three-phase implementation described
herein is not intended to be limiting. More specifically, certain aspects
of the disclosed techniques may be employed on single-phase circuitry
and/or for applications other than power an electric motor. Additionally,
it should be noted that in some embodiments, energy may flow from the
source 12 to the load 14. In other embodiments energy may flow from the
load 14 to the source 12 (e.g., a wind turbine or another generator).
More specifically, in some embodiments, energy flow from the load 14 to
the source 12 may transiently occur, for example, when overhauling a
motor.

[0104] In some embodiments, operation of the switchgear 16 (e.g., opening
or closing of switching devices) may be controlled by control and
monitoring circuitry 18. More specifically, the control and monitoring
circuitry 18 may instruct the switchgear 16 to connect or disconnect
electric power. Accordingly, the control and monitoring circuitry 18 may
include one or more processors 19 and memory 20. More specifically, as
will be described in more detail below, the memory 20 may be a tangible,
non-transitory, computer-readable medium that stores instructions, which
when executed by the one or more processor 18 perform various processes
described. It should be noted that non-transitory merely indicates that
the media is tangible and not a signal. Many different algorithms and
control strategies may be stored in the memory and implemented by the
processor 19, and these will typically depend upon the nature of the
load, the anticipated mechanical and electrical behavior of the load, the
particular implementation, behavior of the switching devices, and so
forth.

[0105] Additionally, as depicted, the control and monitoring circuitry 18
may be remote from the switchgear 16. In other words, the control and
monitoring circuitry 18 may be communicatively coupled to the switchgear
16 via a network 21. In some embodiments, the network 21 may utilize
various communication protocols such as DeviceNet, Profibus, Modbus,
Ethernet, to mention only a few. For example, to transmit signals between
the control and monitoring circuitry 18 may utilize the network 21 to
send make and/or break instructions to the switchgear 16. The network 21
may also communicatively couple the control and monitoring circuitry 18
to other parts of the system 10, such as other control circuitry or a
human-machine-interface (not separately depicted). Additionally or
alternatively, the control and monitoring circuitry 18 may be included in
the switchgear 16 or directly coupled to the switchgear, for example, via
a serial cable.

[0106] Furthermore, as depicted, the electric power input to the
switchgear 16 and output from the switchgear 16 may be monitored by
sensors 22. More specifically, the sensors 22 may monitor (e.g., measure)
the characteristics (e.g., voltage or current) of the electric power.
Accordingly, the sensors 22 may include voltage sensors and current
sensors. These sensors may alternatively be modeled or calculated values
determined based on other measurements (e.g., virtual sensors). Many
other sensors and input devices may be used, depending upon the
parameters available and the application. Additionally, the
characteristics of the electric power measured by the sensors 22 may be
communicated to the control and monitoring circuitry 18 and used as the
basis for algorithmic computation and generation of waveforms (e.g.,
voltage waveforms or current waveforms) that depict the electric power.
More specifically, the waveforms generated based on input the sensors 22
monitoring the electric power input into the switchgear 16 may be used to
define the control of the switching devices, for example, by reducing
electrical arcing when the switching devices open or close. The waveforms
generated based on the sensors 22 monitoring the electric power output
from the switchgear 16 and supplied to the load 14 may be used in a
feedback loop to, for example, monitor conditions of the load 14.

[0107] As described above, the switchgear 16 may connect and/or disconnect
electric power from various types of loads 14, such as the electric motor
24 included in the motor system 26 depicted in FIG. 2. As depicted, the
switchgear 16 may connect and/or disconnect the power source 12 from the
electric motor 24, such as during startup and shut down. Additionally, as
depicted, the switchgear 16 will typically include or function with
protection circuitry 28 and the actual switching circuitry 30 that makes
and breaks connections between the power source and the motor windings.
More specifically, the protection circuitry 28 may include fuses and/or
circuit breakers, and the switching circuitry 30 will typically include
relays, contactors, and/or solid state switches (e.g., SCRs, MOSFETs,
IGBTs, and/or GTOs), such as within specific types of assembled equipment
(e.g., motor starters).

[0108] More specifically, the switching devices included in the protection
circuitry 28 may disconnect the power source 12 from the electric motor
24 when an overload, a short circuit condition, or any other unwanted
condition is detected. Such control may be based on the un-instructed
operation of the device (e.g., due to heating, detection of excessive
current, and/or internal fault), or the control and monitoring circuitry
18 may instruct the switching devices (e.g., contactors or relays)
included in the switching circuitry 30 to open or close. For example, the
switching circuitry 30 may include one (e.g., a three-phase contactor) or
more contactors (e.g., three or more single-pole, single current-carrying
path switching devices).

[0109] Accordingly, to start the electric motor 24, the control and
monitoring circuitry 18 may instruct the one or more contactors in the
switching circuitry 30 to close individually, together, or in a
sequential manner. On the other hand, to stop the electric motor 24, the
control and monitoring circuitry 18 may instruct the one or more
contactors in the switching circuitry 30 to open individually, together,
or in a sequential manner. When the one or more contactors are closed,
electric power from the power source 12 is connected to the electric
motor 24 or adjusted and, when the one or more contactors are open, the
electric power is removed from the electric motor 24 or adjusted. Other
circuits in the system may provide controlled waveforms that regulate
operation of the motor (e.g., motor drives, automation controllers,
etc.), such as based upon movement of articles or manufacture, pressures,
temperatures, and so forth. Such control may be based on varying the
frequency of power waveforms to produce a controlled speed of the motor.

[0110] In some embodiments, the control and monitoring circuitry 18 may
determine when to open or close the one or more contactors based at least
in part on the characteristics of the electric power (e.g., voltage,
current, or frequency) measured by the sensors 22. Additionally or
alternatively, the control and monitoring circuit 18 may receive an
instruction to open or close the one or more contactors in the switching
circuitry 30 from another part of the motor system 26, for example, via
the network 21.

[0111] In addition to using the switchgear 16 to connect or disconnect
electric power directly from the electric motor 24, the switchgear 16 may
connect or disconnect electric power from a motor controller/drive 32
included in a machine or process system 34. More specifically, the system
34 includes a machine or process 36 that receives an input 38 and
produces an output 40.

[0112] To facilitate producing the output 40, the machine or process 36
may include various actuators (e.g., electric motors 24) and sensors 22.
As depicted, one of the electric motors 24 is controlled by the motor
controller/drive 32. More specifically, the motor controller/drive 32 may
control the velocity (e.g., linear and/or rotational), torque, and/or
position of the electric motor 24. Accordingly, as used herein, the motor
controller/drive 32 may include a motor starter (e.g., a wye-delta
starter), a soft starter, a motor drive (e.g., a frequency converter), a
motor controller, or any other desired motor powering device.
Additionally, since the switchgear 16 may selectively connect or
disconnect electric power from the motor controller/drive 32, the
switchgear 16 may indirectly connect or disconnect electric power from
the electric motor 24.

[0113] As used herein, the "switchgear/control circuitry" 42 is used to
generally refer to the switchgear 16 and the motor controller/drive 32.
As depicted, the switchgear/control circuitry 42 is communicatively
coupled to a controller 44 (e.g., an automation controller. More
specifically, the controller 44 may be a programmable logic controller
(PLC) that locally (or remotely) controls operation of the
switchgear/control circuitry 42. For example, the controller 44 may
instruct the motor controller/driver 32 regarding a desired velocity of
the electric motor 24. Additionally, the controller 44 may instruct the
switchgear 16 to connect or disconnect electric power. Accordingly, the
controller 44 may include one or more processor 45 and memory 46. More
specifically, the memory 46 may be a tangible non-transitory
computer-readable medium on which instructions are stored. As will be
described in more detail below, the computer-readable instructions may be
configured to perform various processes described when executed by the
one or more processor 45. In some embodiments, the controller 44 may also
be included within the switchgear/control circuitry 42.

[0114] Furthermore, the controller 44 may be coupled to other parts of the
machine or process system 34 via the network 21. For example, as
depicted, the controller 44 is coupled to the remote control and
monitoring circuitry 18 via the network 21. More specifically, the
automation controller 44 may receive instructions from the remote control
and monitoring circuitry 18 regarding control of the switchgear/control
circuitry 42. Additionally, the controller 44 may send measurements or
diagnostic information, such as the status of the electric motor 24, to
the remote control and monitoring circuitry 18. In other words, the
remote control and monitoring circuitry 18 may enable a user to control
and monitor the machine or process 36 from a remote location.

[0115] Moreover, sensors 22 may be included throughout the machine or
process system 34. More specifically, as depicted, sensors 22 may monitor
electric power supplied to the switchgear 16, electric power supplied to
the motor controller/drive 32, and electric power supplied to the
electric motor 24. Additionally, as depicted, sensors 22 may be included
to monitor the machine or process 36. For example, in a manufacturing
process, sensors 22 may be included to measure speeds, torques, flow
rates, pressures, the presence of items and components, or any other
parameters relevant to the controlled process or machine.

[0116] As described above, the sensors 22 may feedback information
gathered regarding the switchgear/control circuitry 42, the motor 24,
and/or the machine or process 36 to the control and monitoring circuitry
18 in a feedback loop. More specifically, the sensors 22 may provide the
gathered information to the automation controller 44 and the automation
controller 44 may relay the information to the remote control and
monitoring circuitry 18. Additionally or alternatively, the sensors 22
may provide the gathered information directly to the remote control and
monitoring circuitry 18, for example via the network 21.

[0117] To facilitate operation of the machine or process 36, the electric
motor 24 converts electric power to provide mechanical power. To help
illustrate, an electric motor 24 may provide mechanical power to various
devices, as described in the non-limiting examples depicted in FIGS.
4A-4D. For example, as depicted in FIG. 4A, the electric motor 24 may
provide mechanical power to a fan 47. More specifically, the mechanical
power generated by the electric motor 24 may rotate blades of the fan 47
to, for example, vent a factory. Accordingly, the switchgear/control
circuitry 42 may control operation (e.g., velocity) of the fan 47 by
controlling electric power supplied from the power source 12 to the
electric motor 24. For example, the switchgear/control circuitry 42 may
decrease electric power supplied to the motor 24 to reduce velocity of
the fan 47. On the other hand, the switchgear/control circuitry 42 may
increase electric power supplied to the motor 24 to increase velocity of
the fan 47. As depicted, a sensor 22 may also be included on the fan 47
to provide feedback information regarding operation of the fan 22, such
as temperature, velocity, torque, or position, which may be used to
adjust operation of the fan 47. In other words, operation of the fan 47
may be adjusted in a feedback loop.

[0118] Additionally, as depicted in FIG. 4B, the electric motor 24 may
provide mechanical power to a conveyer belt 48. More specifically, the
mechanical power generated by the electric motor 24 may rotate the
conveyer belt 48 to, for example, move a package along the conveyer belt
48. Accordingly, the switchgear/control circuitry 42 may control
operation (e.g., acceleration, velocity, and/or position) of the conveyer
belt 48 by controlling electric power supplied from the power source 12
to the electric motor 24. For example, the switchgear/control circuitry
42 may start the conveyer belt 48 by supplying electric power to the
motor 24. On the other hand, the switchgear/control circuitry 42 may stop
the conveyer belt 48 at a specific position by ceasing electric power
supplied to the motor 24. As depicted, a sensor 22 may also be included
on the conveyer belt 48 to provide feedback information regarding
operation of the conveyer belt 48, such as temperature, velocity, torque,
or position, which may be used to adjust operation of the conveyer belt
48. In other words, operation of the conveyer belt 48 may be adjusted in
a feedback loop.

[0119] Furthermore, as depicted in FIG. 4C, the electric motor 24 may
provide mechanical power to a pump 50. More specifically, the mechanical
power generated by the electric motor may drive the pump 50 to, for
example, move a fluid (e.g., gas or liquid). Accordingly, the
switchgear/control circuitry 42 may control operation (e.g., pumping
rate) of the pump 50 by controlling electric power supplied from the
power source 12 to the electric motor 24. For example, the
switchgear/control circuitry 42 may increase electric power supplied to
the motor 24 to increase the pumping rate of the pump 50. On the other
hand, the switchgear/control circuitry 42 may decrease electric power
supplied to the motor 24 to decrease the pumping rate of the pump 50. As
depicted, a sensor 22 may also be included on the pump 50 to provide
feedback information regarding operation of the pump 50, such as
temperature or pumping rate, which may be used to adjust operation of the
pump 50. In other words, operation of the pump 50 may be adjusted in a
feedback loop.

[0120] As described above, the electric motor 24 may be used to facilitate
a machine or process 36. To help illustrate, FIG. 4D depicts a chiller
system 52 that may be used in a process to cool a circulated fluid, such
as in an air conditioning or refrigeration system, which includes a
chiller 54 and a fluid handler 56. More specifically, the fluid handler
56 circulates the fluid (e.g., air or water) into the chiller 54 to cool
the fluid by exchanging heat with a refrigerant in the chiller 54. To
facilitate cooling the fluid, the chiller 54 includes an evaporator 58, a
condenser 60, an expansion device 62, and a compressor 64, which pumps
the refrigerant (e.g., coolant) in the chiller 54. Accordingly, as
depicted, the compressor 64 includes the electric motor 24 and the pump
50.

[0121] In operation, the compressor 64 compresses refrigerant gas that is
condensed in the condenser 60. In the condenser 60, heat from the
refrigerant gas is exchanged with cooling water or air, which accepts the
heat required for the condensation phase change. In the expansion device
62, the flow of the liquid refrigerant is restricted to reduce the
pressure of the refrigerant. In some embodiments, some of the refrigerant
may vaporize and absorb heat from surrounding liquid refrigerant to
further lower temperature. In the evaporator 58, the latent heat of
vaporization of the refrigerant absorbs heat from the fluid circulated
from the fluid handler 56 to cool the fluid (often air).

[0122] More specifically, one or more electric motors 24 may drive the
compressor 64 (and/or the pump 50). For example, when the chiller 54 is a
centrifugal chiller, the electric motor 24 may rotate an impeller to
compress (e.g., accelerate) refrigerant gas in the chiller 54.
Accordingly, the switchgear/control circuitry 42 may control operation of
the compressor 64 by controlling electric power supplied to the electric
motor 24 from the power source 12. For example, to increase the flow rate
(e.g., compression) of refrigerant gas, the switchgear/control circuitry
42 may increase electric power supplied to the electric motor 24 to
increase torque and/or velocity compressor. In some embodiments, the
switchgear/control circuitry 42 may adjust the electric power supplied by
reconfiguring windings of the electric motor 24, for example, from a wye
configuration to a delta configuration.

[0123] Mechanical loads driven by motors may have a wide range of physical
and dynamic characteristics that may affect the strategies for powering
the motors. For example, chiller applications may result in highly
inertial loads (e.g., that start slowly and with high torque
requirements, and that stop quickly once power is removed). Other
inertial loads may be difficult to stop and may impose particular torque
demands when stopping. Fans will typically have known torque/speed or
power curves, as may certain types of pumps. Given that any desired load
may be driven by the technology described here, corresponding strategies
may be implemented for controlling the application of power.

[0124] It should also be noted that, while particular emphasis is placed
on powering electric motors by the present technologies, many other loads
may benefit from the advances proposed. These may include, but are not
limited to, transformers, capacitor banks, linear and other actuators,
various power converters, and so forth.

[0125] Basic Point-On-Wave (POW) Switching

[0126] As discussed in the above examples, the switchgear/control
circuitry 42 may control operation of a load 14 (e.g., electric motor 24)
by controlling electric power supplied to the load 14. For example,
switching devices (e.g., contactors) in the switchgear/control circuitry
42 may be closed to supply electric power to the load 14 and opened to
disconnect electric power from the load 14. However, as discussed above,
opening (e.g., breaking) and closing (e.g., making) the switching devices
may discharge electric power in the form of electric arcing, cause
current oscillations to be supplied to the load 14, and/or cause the load
14 to produce torque oscillations.

[0127] Accordingly, some embodiments of the present disclosure provide
techniques for breaking a switching device in coordination with a
specific point on an electric power waveform. For example, to reduce
magnitude and/or likelihood of arcing, the switching device may open
based on a current zero-crossing. As used herein, a "current
zero-crossing" is intended to describe when the current conducted by the
switching device is zero. Accordingly, by breaking exactly at a current
zero-crossing, the likelihood of generating an arc is minimal since the
conducted current is zero.

[0128] However, closing the switching device is generally
non-instantaneous and the conducted electric power changes rapidly. As
such, it may be difficult to break the switching device exactly on the
current zero-crossing. In other words, even when aiming for the current
zero-crossing it is possible that the switching device actually breaks
slightly before or slightly after the current zero-crossing. However,
although the current may be relatively low slightly after the current
zero-crossing, the magnitude may be increasing and, thus, cause arcing
with increased magnitude. On the other hand, the magnitude of the current
slightly before the current zero-crossing is low and decreasing. As such,
the magnitude of any produced arcing may be small and be extinguished
when reaching the current zero-crossing. In other words, the switching
device may be opened based at least in part on a current zero-crossing
such that the switching device breaks slightly before or at the current
zero-crossing.

[0129] Similarly, some embodiments of the present disclosure provide
techniques for breaking a switching device in coordination with a
specific point on an electric power waveform. For example, to reduce
magnitude of in-rush current and/or current oscillation, the switching
device may close based on a predicted current zero-crossing. As used
herein, a "predicted current zero-crossing" is intended to describe where
a current zero-crossing would have occurred assuming the switching device
was closed and in steady state. In other words, the predicted current
zero-crossing may be a multiple of 180.degree. from a subsequent steady
state current zero-crossing. Accordingly, by making exactly at a
predicted zero-crossing, the conducted current may increase more
gradually, thereby reducing magnitude of in-rush current and/or current
oscillation.

[0130] However, when the switching device is open, the current supplied to
the switching device is approximately zero while the voltage is
approximately equal to the source voltage. Since the voltage and the
current generally a fixed phase difference in steady-state, the voltage
supplied to the switching device may be used to determine the predicted
current zero-crossing. For example, when the voltage leads the current by
90.degree., a current zero-crossing occurs 90.degree. after a
line-to-line voltage zero-crossing, which may also be 60.degree. after a
phase voltage zero-crossing. As used herein, a "line-to-line voltage
zero-crossing" is intended to describe when voltage supplied to a
switching device is zero relative to another phase and a "phase voltage
zero-crossing" is intended to describe when voltage supplied to the
switching device is zero relative to ground. Accordingly, the predicted
current zero-crossing may occur 90.degree. after the line-to-line voltage
zero-crossing when the voltage is at a maximum.

[0131] Since opening the switching device is generally non-instantaneous
and the conducted electric power changes rapidly, it may be difficult to
make the switching device exactly on the predicted current zero-crossing.
In other words, even when aiming for the predicted current zero-crossing
it is possible that the switching device actually makes slightly before
or slightly after the current zero-crossing. However, since the magnitude
of the current changes more gradually at the predicted current
zero-crossing, magnitude of in-rush current and/or current oscillation
may be reduced. In other words, the switching device may be closed based
at least in part on a predicted current zero-crossing such that the
switching device makes slightly before, slight after, or at the predicted
current zero-crossing.

[0132] Although some embodiments describe breaking a switching device
based on a current zero-crossing or making the switching device based on
a predicted current zero-crossing, it should be understood that the
switching devices may be controlled to open and close at any desired
point on the waveform using the disclosed techniques. To facilitate
opening and/or closing at a desired point on the waveform, one or more
switching devices may be independently controlled to selectively connect
and disconnect a phase of electric power to the load 14. In some
embodiments, the one or more switching devices may be a multi-pole,
multi-current carrying path switching device that controls connection of
each phase with a separate pole. More specifically, the multi-pole,
multi-current carrying path switching device may control each phase of
electric power by movement of a common assembly under the influence of a
single operator (e.g., an electromagnetic operator). Thus, in some
embodiments, to facilitate independent control, each pole may be
connected to the common assembly in an offset manner, thereby enabling
movement of the common assembly to affect one or more of the poles
differently.

[0133] In other embodiments, the one or more switching devices may include
multiple single pole switching devices. As used herein a "single pole
switching device" is intended to differentiate from a multi-pole, multi
current-carrying path switching device in that each phase is controlled
by movement of a separate assembly under influence of a separate
operator. In some embodiments, the single pole switching device may be a
single pole, multi-current carrying path switching device (e.g., multiple
current carrying paths controlled by movement of a single operator) or a
single-pole, single current-carrying path switching device, which will be
described in more detail below.

[0134] As described above, controlling the making (e.g., closing) of the
one or more switching devices may facilitate reducing magnitude of
in-rush current and/or current oscillations, which may strain the load
14, the power source 12, and/or other connected components. As such, the
one or more switching devices may be controlled such that they make based
at least in part on a predicted current zero-crossing (e.g., within a
range slightly before to slightly after the predicted current zero
crossing).

[0135] To help illustrate, closing the switching devices to provide
three-phase electric power to an electric motor 24 in a wye configuration
is described in FIGS. 5A-5C. More specifically, FIG. 5A illustrates the
voltage of three-phase electric power (e.g., a first phase voltage curve
66, a second phase voltage curve 68, and a third phase voltage curve 70)
provided by a power source 12. FIG. 5B illustrates the line to neutral
voltage supplied to each terminal (e.g., first terminal voltage curve 72,
second terminal voltage curve 74, and third terminal voltage curve 76) of
the electric motor 24. FIG. 5C illustrates line current supplied to each
winding (e.g., first winding current curve 77, second winding current
curve 78, and third winding current curve 80) of the electric motor 24.
As described above, the waveforms depicted in FIGS. 5A-5C may be
determined by control and monitoring circuitry 18 based on measurements
collected by the sensors 22.

[0136] As depicted, between t0 and t1, electric power is not connected to
the electric motor 24. In other words, each of the switching devices is
open. At t1, one or more switching devices are closed to start current
flow from the power source 12 in two phases (e.g., a first phase and a
second phase) of the electric motor 24. To minimize inrush current and/or
current oscillations, a first phase and a second phase are connected
based upon a predicted current zero-crossing. Accordingly, as depicted in
FIG. 5A, the first phase and the second phase are connected when the
line-to-line voltage of the first phase (e.g., first phase voltage curve
66) and the second phase (e.g., a second phase voltage curve 68) is at a
maximum (e.g., 90.degree. after a line-to-line voltage zero-crossing).
Once connected, the first phase of the electric power flows into the
first winding of the electric motor 24, the second phase of the
electrical flows into the second winding of the electric motor 24, and
the third winding of the electric motor 24 is at an internal neutral
(e.g., different from line neutral), as depicted in FIG. 5B.
Additionally, since the two phases are connected at a predicted current
zero-crossing, the current supplied to the first winding (e.g., first
winding current curve 77) and the second winding (e.g., second winding
current curve 78) start at zero and gradually increase, as depicted in
FIG. 5C, thereby reducing magnitude of in-rush current and/or current
oscillations supplied to the first and second windings.

[0137] After the first two phases are connected, at t2, the one or more
switching devices are closed to connect a third phase of the electric
power to the electric motor 24. Similar to the first phase and the second
phase, to minimize inrush current and/or current oscillations, the third
phase is also connected based upon a predicted current zero-crossing.
Accordingly, as depicted in FIG. 5A, the third phase is connected when
sum of line-to-line voltage between the first phase (e.g., first phase
voltage curve 66) and the third phase (e.g., third phase voltage curve
70) and the line-to-line voltage between the second phase (e.g., second
phase voltage curve 68) and the third phase (e.g., third phase voltage
curve 70) is at a maximum (e.g., a predicted current zero-crossing),
which occurs when the line-to-line voltage between the first phase and
the second phase is at a minimum and third phase is at a maximum.

[0138] It should be noted that although the third phase is depicted as
being connected at the first such subsequent occurrence, the third phase
may additionally or alternatively be connected at any subsequent
occurrence, for example at t3. Once connected, the third phase of the
electric power flows into the third winding of the electric motor 24, as
depicted in FIG. 5B. Additionally, since the third phase is connected
based upon a predicted current zero-crossing, the third winding current
80 gradually changes from zero, as depicted in FIG. 5C, thereby reducing
magnitude of in-rush current and/or current oscillations supplied to the
third winding.

[0139] Additionally, as described above, controlling the breaking (e.g.,
opening) of the one or more switching devices may facilitate reducing
likelihood and/or magnitude of arcing, which may strain and/or wear
contactor pads in the switching devices and/or other connected
components. As such, the one or more switching devices may be controlled
such that they break based at least in part on a current-zero crossing
(e.g., within a range slightly before to at the current zero-crossing
across that switching device).

[0140] To help illustrate, opening the switching devices to disconnect
three-phase electric power from an electric motor 24 is described in FIG.
6. More specifically, FIG. 6 depicts the current supplied to the windings
(e.g., first winding current curve 77, second winding current curve 78,
and third winding current curve 80) of the electric motor 24. As
described above, the waveform depicted in FIG. 6 may be determined by
control and monitoring circuitry 18 based on measurements collected by
the sensors 22.

[0141] As depicted, prior to t4, electric power is connected to the
electric motor 24. In other words, each of the switching devices is
closed. At t5, one or more of the switching devices is opened to
disconnect the third phase of the electric power from the electric motor
24. As described above, to minimize arcing, the third phase disconnected
is based at least in part on a current zero-crossing in the third phase
of electric power. Accordingly, as depicted, the third phase is
disconnected when the current supplied to the third winding (e.g., third
winding current curve 80) is approximately zero. Once disconnected, the
current supplied to the second winding current the first winding current
adjust to the removal of the third phase.

[0142] After the third phase is disconnected, the one or more of the
switching devices are opened to disconnect the other two phases (e.g.,
the first phase and the second phase) of electric power to the electric
motor 24 at t6. Similar to disconnecting the third phase, to minimize
arcing, the first phase is disconnected based at least in part on a
current zero-crossing in the first phase of electric power and the second
phase is disconnected based at least in part on a current zero-crossing
in the second phase of electric power. Accordingly, as depicted, the
first phase and the second phase are disconnected when current supplied
to the second winding (e.g., second winding current curve 78) and the
first winding (e.g., first winding current curve 77) are approximately
zero. Once disconnected, the electric power supplied to the electric
motor 24 begins to decrease. It should be noted that although the first
phase and the second phase are depicted as being disconnected at the
first subsequent current zero-crossing, the first and second phase may
additionally or alternatively be disconnected at any subsequent current
zero-crossings.

Single-Pole, Single Current-Carrying Path Switching Device

[0143] FIGS. 7-24 depict a presently contemplated arrangement for
providing a single-pole, single current-carrying path switching device.
The device may be used in single-phase applications, or very usefully in
multi phase (e.g., three-phase) circuits. It may be used alone or to form
modular devices and assemblies such as for specific purposes as described
below. Moreover, it may be designed for use in POW power application, and
in such applications, synergies may be realized that allow for very
compact and efficient designs due, as least in part, to the reduced
operator demands, reduced arcing, and improved electromagnetic effects
during the application of current through the device.

[0144] It should be noted that various embodiments of the single-pole
switching devices may be used in single current-carrying path
applications and also in multi current-carrying path applications. That
is, references to single-pole switching devices throughout the disclosure
may refer to single-pole, single current carrying path switching devices,
single-pole, multiple current carrying path switching devices, or some
combination thereof. In some embodiments, a single-pole, multiple
current-carrying path switching device may allow for the repurposing of
certain devices as modular three-phase circuits. For example, a
single-pole, multiple current-carrying path may refer to a switching
device with three current-carrying paths that have been interconnected to
provide a single phase of power. Additionally, in some embodiments, three
single-pole, single current-carrying path switching devices may each be
configured to provide a separate phase of power (e.g., three-phase) and
can be independently and/or simultaneously controlled in various
beneficial configurations, as described in detail below. It should be
understood, that the single-pole switching devices may be modularly
configured to provide any number of power phases.

[0145] FIG. 7 illustrates a switching device 82 designed for use in
certain of the applications described in the present disclosure. In the
embodiment illustrated, a switching device is a single-pole, single
current-carrying path device in the form of a contactor 84. The contactor
84 generally includes an operator section 86 and a contact section 88. As
described more fully below, the operator section includes components that
enable energization and de-energization of the contactor to complete and
interrupt a single current-carrying path through the device. The section
88 includes components that are stationary and other components that are
moved by energization and de-energization of the operator section to
complete and interrupt the single-carrying path. In the illustrated
embodiment, the upper conductive section has an upper housing 90, while
the operator section has a lower housing 92. The housings fit together to
form a single unitary housing body. In the illustrated embodiment flanges
94 extend from the lower housing allowing the device to be mounted in
operation. Other mounting arrangements may certainly be envisaged. A
line-side conductor 96 extends from the device to enable connection to a
source of power. A corresponding load-side conductor 98 extends from an
opposite side to enable the device to be coupled to a load. In other
embodiments, conductors may exit the housing 90 and 92 in other manners.
In this illustrated embodiment the device also includes an upper or
top-side auxiliary actuator 100 and a side mount auxiliary actuator 102.

[0146] FIG. 8 illustrates certain of the mechanical, electrical and
operational components of the contactor in an exploded view. As shown,
the operator section is mounted in the lower housing 92 and includes an
operator designated generally by reference numeral 104 which itself is a
collection of components including a magnetic core comprised of a yoke
106 and a central core section 108. A return spring 110 is mounted
through the central core section 108 as described more fully below for
biasing movable contacts towards an open position. An operator coil 112
is mounted around the core section 108 and between upturned portions of
the yoke 106. As will be appreciated by those skilled in the art, the
coil 112 will typically be mounted on a bobbin and is formed of multiple
turns of magnet wire, such as copper. The operator includes leads 114,
which in this embodiment extend upwardly to enable connection to the
operator when the components are assembled in the device. As will also be
appreciated by those skilled in the art, the core, including the yoke and
central core section, along with the coil 112 form an electromagnet
which, when energized, attracts one or more parts of the movable contact
assembly described below, to shift the device between an open position
and a closed position.

[0147] A movable contact assembly 116 similarly includes a number of
components assembled as a sub-assembly over the operator. In the
embodiment illustrated in FIG. 8, the movable assembly includes an
armature 118 that is made of a metal or material that can be attracted by
flux generated by energization of the operator. The armature is attached
to a carrier 120 which typically is made of a non-conductive material,
such as plastic or fiberglass, or any other suitable electrically
insulating material. A conductor assembly 122 is mounted in the carrier
and is moved upwardly and downwardly by movement of the carrier under the
influence of electromagnetic flux that draws the armature downwardly,
and, when the fluxes are removed, the entire assembly may be moved
upwardly under the influence of the return spring 110 mentioned above.

[0148] The device further includes a stationary contact assembly 124. In
the illustrated embodiment, this contact assembly is formed of multiple
hardware components, including a mounting assembly 126 that is fitted
between the lower housing 92 and the upper housing 90. This mounting
assembly will typically be made of an electrically non-conductive
material, and it includes various features for allowing the mounting of
the line and load-side conductors 96 and 98. It may be noted that the
structure illustrated in FIG. 8 has been rotated 180 degrees as compared
to that of FIG. 7. Each conductor includes a contact pad that comes into
contact with a corresponding contact pad of the movable contact assembly
when the device is closed or "made". Moreover, turnbacks 128 are provided
on each conductor and may be screwed or riveted into place, or attached
by any other suitable method, and at least partially span the contact pad
of the corresponding conductor. In the final assembly, these turnbacks
are fitted adjacent to a series of splitter plates or shunts 130 on
either side. As described more fully below, when the device makes or
breaks, any arcing that occurs can be driven to the turnbacks and
splitter plates where the arc is divided into several smaller arcs and
ionized particles and hot gasses are cooled and routed toward the
exterior device.

[0149] FIGS. 9 and 10 illustrate the same device assembled in top and
bottom perspective views, with certain of the components removed,
including certain housing sections to illustrate the interior components
and their interior connection. In particular, as shown in FIG. 9, the
coil 112 of the operator is positioned in a lower location, although in
practice the device may be mounted in various orientations. The mounting
assembly 126 holding the line and load-side conductors is fitted above
the operator coil and the movable contact assembly 116 is position above
the mounting assembly such that contact pads of movable contacts within
this assembly are positioned in facing relation to corresponding contact
pads on the conductors. More detail regarding the various components of
these assemblies is provided below. As can also be seen in FIGS. 9 and
10, guides 132 may be formed, such as in the mounting assembly 126 for
receiving the terminals of the operator coil. In this illustrated
embodiment the terminals extend upwardly and are formed so that plug-in
connections can be made to the operator coil. As will be appreciated by
those skilled in the art, in operation, a signal that energizes the
operator coil is provided by way of the terminals, and typical signals
may include alternating current (A/C) or direct current (DC) signals,
such as 24 or 48 vDC signals. Although AC signals may be provided for the
operator coil, in some applications, such as POW energization strategies,
predictability in times of closure and opening are provided by DC
signals. In some alternative embodiments the terminals, or leads for the
operator coil may be caused to exit other locations in device, such as
through the lower housing. Such applications may provide for plug-in
mounting of the contactor or any similar switching device such that
contacts are made for at least the operator by simply mounting the device
on a suitable base. In some arrangements it may also be suitable to allow
for power, both line and load, to be made through such a base.

[0150] FIGS. 11 and 12 provide additional detail of the currently
contemplated single-pole, single current-carrying path switching device.
As shown in FIG. 11, the operator coil 112 is disposed within the yoke
106 such that the yoke channels flux generated by operator coil when
energized. In this arrangement, the return spring 110 is provided around
an alignment pin 134 that is fixed to and moves with the movable contact
assembly, and specifically in this arrangement is mounted to the carrier.
FIG. 11 illustrates the foregoing components in a de-energized or open
position of the device. In this position, the movable contact assembly is
distanced from the stationary contacts of the conductors so that
current-carrying path through the device is interrupted. The device is
thus electrically open.

[0151] FIG. 12 illustrates the same components, in a view in which certain
of them have been shown in section to illustrate their inter-relationship
and operation. Here again, the device is shown in an electrically open
position that will exist when the operator is de-energized prior to
making or after breaking. As shown in FIG. 12, in the de-energized
position, the entire movable contact assembly is held in a raised
position by the return spring 110. Here again, the device may be oriented
differently so that the terms "raised" or "lowered" or similar terms are
intended as only given the orientation shown in the figures. In this
position, the armature 118 is separated from the operator assembly, in
particularly from the yoke 108 and the core 108. The carrier 120 holds
the conductor assembly 122 spaced from the contact pads of the line and
load-side conductors 96 and 98. The assembly is illustrated as including
guides 132 (see FIGS. 9 and 10) through edge the terminals 114 may be
routed.

[0152] In the currently contemplated embodiment, to reduce size and weight
but to provide an excellent working structure, a guide or alignment pin
134 is provided in the movable assembly. The pin may be secured in place
by any suitable means, such as a clip or retaining ring in the carrier.
The pin is recessed within the carrier to provide the desired degree of
perpendicularly and alignment with the other components of the movable
structure. The operator assembly, on the other hand, comprises one or
more core windings 136 which are made of a series of electrically
insulated conductive wire, such as copper. The wires typically wound on a
bobbin 138 which is placed between the yoke 106 and the core section 108.
The core assembly is typically formed as a separate component which is
assembled with the other elements of the other elements of the operator
during manufacture. In the illustrated embodiment, the core section 108
is formed as a cylindrical structure having a central aperture 140 for
receiving the alignment pin 134. An extension 142 of this core section is
affixed to a lower opening in the yoke 106, such as by staking,
threading, or any suitable means. The aperture 140 comprises at least two
sections, including a central alignment section 144 that is dimensioned
to fit relatively snuggly with the alignment pin, but to allow for easy
movement of the alignment pin therein, providing the desired alignment
function. An upper recess 146 is somewhat enlarged in forms of shoulder
within the core section to receive the return sprig 110 and to form a
foundation against which the return spring bears during operation. In the
depicted embodiment, the return spring 110 is provided in a convenient
location, but may be provided in other locations in other embodiments.

[0153] The upper portion of the carrier 120 includes a window 150 in which
the conductor assembly 122 is positioned. The window is contoured to
receive and to hold in place a movable conductor biasing spring 152 that
enables some movement of the conductor assembly 122 as it comes into
contact with the line and load-side conductors 196 and 198. As will be
appreciated by those skilled in the art, in the illustrated embodiment,
the conductor assembly 122 includes a turnback element, a conductive
bridge or spanner, and contact pads affixed to this spanner. The spanner
will typically be made of a highly conductive material, such as copper,
and the contact pads will be made of a conductive material that is
nevertheless resistant to arcing that may occur, such as silver,
silver/tin oxide, silver nickel alloys, and so forth.

[0154] The line and load-side conductors 96 and 98 may be mounted to the
mounting assembly 126 in any suitable manner, such as by screws or rivets
154. As can be best seen in the exploded view of FIG. 8, contact pads of
the line and load-side conductors are positioned to come into contact
with the contact pads of the movable conductor assembly when the device
is closed or "made". The turnbacks 128 fit around this contact pad and
are themselves are secured by fasteners. One or more insulative elements,
such as synthetic membranes may be placed between the turnbacks 128 and
the conductors 96 and 98 when desired. In the illustrated embodiment
bumps 156 are formed on the turnbacks to promote migration of any arcs
that are formed during operation of the device.

[0155] The elements of the movable contact assembly are illustrated in
greater detail in FIG. 13. Here again, the conductor assembly 122 may
include an upper auxiliary actuator 100, where desired. A side auxiliary
actuator 102 may also be included. The assembly itself is formed around
the conductor 158 which forms the bridge for the structure. Contact pads
160 are affixed to a lower side of this conductor and come into contact
with the stationary contact pads of the line and low-side conductors when
the device is closed or energized. The carrier assembly 122 itself also
includes a base 164 to which the armature 118 is secured by appropriate
fasteners 166. Again, the alignment pin 134 extends downwardly from the
base 164 of the carrier.

[0156] Additionally, a turnback 162 is formed in a metallic element that
rests adjacent to the conductive span 158. In the illustrated embodiment
the turnback 162 also contacts the conductor biasing spring 152 to hold
the movable conductors in a lower position in the window 150. In some
embodiments, the turnback 162 may shape the magnetic field during opening
by providing an alternate path for the current. More specifically, the
arc may be attached up onto a face 163 of the turnback 162 and stay there
during the arcing event. In this manner, the arcing experienced by the
contactor pads 160 may be reduced, thereby enabling the ionized
atmosphere around the contact pads 160 to regain their dielectric
strength

[0157] FIG. 14 illustrates the foregoing structure in the energized or
shifted position. This position corresponds to energization of the
operator coil, typically by application of a DC voltage. So long as the
coil is energized, the coil generates a flux that is channeled by the
yoke 106 and core 108 of the operator assembly, drawing the armature
toward the operator assembly, shifting the entire movable contact
assembly downwardly. Thus, in FIG. 14 the armature 118 is illustrated in
a downward position adjacent to the yoke 106. The alignment pin has
guided the movable assembly in its motion, and protrudes further into the
alignment portion 144 of the aperture in the core section 108. The return
spring is shown compressed. The movable contacts, hidden here behind the
fasteners of the turnbacks in the stationary contact assembly are in
contact to complete a current carrying path through the device. In the
presently contemplated embodiment, a single current carrying path is
defined through the device that includes the line-side conductor 96, the
load-side conductor 98, the contact pads of these conductors, the movable
contact pads of the movable contact assembly, and the conductive spanner
of the movable contact assembly. The device is thus a single-pole device
that is suitable for passing current of a single phase of AC power (or DC
power).

[0158] Certain presently contemplated details of this assembly are
illustrated in FIGS. 15 and 16. As shown in FIG. 15, to promote
saturation of the yoke 106, upper ends of the yoke may have a reduced
dimension 170 in a region where they come into contact with or are close
to the armature 118 when shifted. Such saturation may facilitate holding
of the movable assembly in the shifted position while reducing required
holding current in the coil. As shown in FIG. 16, moreover, a gap 172 may
be formed between the upper surface of the central core section 108 of
the operator assembly and the armature 118. Such gaps may be formed by
air spacing, insulating elements, or by any similar means. Such gaps may
aid in avoiding residual flux in the armature 118, yoke 106 and/or core
108 that may otherwise preclude or slow the separation or movement of the
movable assembly upon de-energization of the operator coil.

[0159] FIG. 17A illustrates a presently contemplated alternative
configuration in which current may be sensed by the effects of the
current on signals through the operator coil itself. That is, before the
device is shifted or energized to make or close the device, no current
should flow between the line and low-side conductors. Once the device is
shifted, however, current may flow through the single current-carrying
path as described herein. When current does flow, various mechanisms may
be envisaged for sensing the current, including separate current sensors,
which may be internal or external to the switching device. It is
presently contemplated, however, that certain elements of the structure
may themselves permit sensing of the main current through the single
current-carrying path. Such sensing may, for example, be performed by
monitoring current through the operator coil described below. The current
to the operator coil may be perturbed in detectable ways by current
through the single current-carrying path. Such perturbations may be
evaluated by the coil control circuitry and used as an indication of the
main current through the device. In the illustration of FIG. 17A, the
armature 118 may provide sufficient coupling of flux generated by the
main current through the device with current through the operator coil to
enable such sensing. Where enhanced sensing is desired, it is possible to
design the armature 118 to promote the sensing, such as by the inclusion
of wings 168 or other structures that tend to enhance the uptake of flux
through the armature that may be generated by the current through the
main current-carrying path.

[0160] An alternative or complimentary arrangement for sensing current is
illustrated in FIG. 17B. In this arrangement, one or more sense windings
174 are provided on the operator coil 112. The sense winding may be made
of a similar or different material, and will typically not require more
than one or a few turns. Where desired, a secondary groove may be
provided in the bobbin discussed above to receive the sense winding. The
sense winding, where provided, will have lead as illustrated in FIG. 17B
that will be coupled to measurement circuitry used to detect current
through the main current-carrying path of the device.

[0161] The contactor illustrated in the figures also includes integral
structures for routing plasma and hot gasses and facilitating their
migration out of the device where desired. As illustrated in FIGS. 18 and
19, these might include features of the splitter plates 130 and the upper
housing. As shown in FIG. 18, for example, a current design for the
splitter plates 130 includes stake ridges that allow the plates to be
pressed into place within the upper housing and held into place,
preventing their withdrawal. A lower recess 178 is formed in each plate,
and upper recesses 180 are formed that enable the passage of plasma and
hot gasses during opening and closing of the device. As best illustrated
in FIG. 19, the upper housing may include alignment features, such as
recesses 180 that may also enable the passage of operator coil leads,
where such designs are used. Within the upper housing, plate guides 182
may be formed that receive the splitter plates therebetween, and hold the
splitter plates in spaced relation with one another. On ends of the
interior surface of the upper housing, gas guides 184 may be formed that
are separated from one another by grooves 186. These may be placed in
general alignment with the recesses 180 formed in the splitter plates.
Gasses may thus be channeled upwardly around the movable contact
assembly, through the upper recesses 180, which form passage ways with
the upper interior wall of the upper housing, and then downwardly through
the grooves 186. The gasses may exit gaps formed between line and
load-side conductors and the upper housing. In the illustrated
embodiment, the upper housing (and where desired the lower housing and
even the mounting assembly for the stationary contact assembly) may be
bilaterally symmetrical so that its orientation is arbitrary, greatly
facilitating assembly of the device. Such innovations may also facilitate
ease of manufacturing and reduced number of different parts.

[0162] FIG. 20 illustrates a cross-sectional view of the single
current-carrying path switching device. More specifically, when the
switching device is closed (e.g., core windings 136 are energize), as
indicated by arrow 188 in FIG. 20, a single current-carrying path is
established through the device when closed, allowing for single-pole
operation. As discussed in greater detail below, the device may be made
much smaller physically than previous devices of the same type. This is
particularly true owing to the mechanical design of the components. The
design around a single-pole strategy rather than a three-phase strategy,
and so forth. The device may be particular reduced in size and mass by
the use of POW switching strategies which greatly reduce arcing and wear
within the device. As also noted elsewhere in the present discussion,
where the switching devices used for three-phase applications, and POW
switching strategies are employed, adjusting order and/or timing of
opening/closing switching devices may greatly prolong the life of the
device while allowing for reduced size and mass. The reduction in size
and mass affectively also reduces the cost of the individual components,
particularly the relatively expensive conductive materials used. Further,
smaller devices may also reduce the electrical enclosure used to house
these components and, thus, reduce the amount of space within a factory
or facility occupied by such components.

[0163] On the other hand, when the switching device opens from the closed
position plasma and/or gasses may be generated. Accordingly, as indicated
by arrow 190, the plasma and/or gasses are routed upwardly through
passageways and the splitter plates 130 and then downwardly through
grooves in the upper housing 90. In fact, such routing facilitates
interruption of current through the device by the action of the splitter
plates 130, and also significantly cools plasma and gasses as they are
routed through the device and exit.

[0164] The single-pole, single current-carrying path device described
above may be used in a variety of applications and ways. For example, the
device may be energized by controlled DC currents as described elsewhere
in the present disclosure. Such control facilitate carefully timed
switching, such as for POW switching strategies. The device may be used
for single-phase switching or multi-phase switching, such as in
three-phase systems. The reduced size, weight and mass of the device
discussed above greatly facilitate the assembly of the device in various
ways, promoting a modular approach to a system design. As discussed
below, such modularity may enable the construction of a wide range of
complex devices that have heretofore been designed with three-phase
contactors, relays and other switches, complex wiring, complex assembly,
and so forth.

[0165] One mechanism for enabling the interconnection of the devices may
be based around the use of mechanical interlocks that are positioned
between mated devices. FIGS. 21-24 illustrate the use such interlocks. In
the illustration of FIG. 21, two switching devices 82 and 82' are shown
positioned side-by-side with an assembly 192. The assembly includes an
interlock 194 that is positioned between, secured to and that interfaces
with the side auxiliary actuators of the devices as described above. As
shown in FIG. 22, various assemblies of this type may be envisaged. In
the more complex assembly of FIG. 22, a number of switching devices are
positioned side-by-side, with interlocks 194 being placed between certain
devices that should not be switched or energized at the same time. Owing
to the particular construction and design of the devices it has been
found that reduced distances may be allowed while nevertheless respecting
requirements of electrical codes. Where desired, to define the desired
circuitry, one or more conjunctive jumpers 196 may be routed between line
and/or load-side conductors as generally shown in FIG. 22. Where desired,
insulated materials may be placed between such jumpers to enable
definition of complex circuitry that includes the current-carrying paths
defined by the modular devices. Pairs 198 of the devices may be
positioned side-by-side, while other pairs are positioned side-by-side
with the interlocks 194 provided therebetween.

[0166] Again, the interlocks may enable mechanical control of the modular
switching devices, and in particular prevent two switching devices from
being closed at the same time. As will be appreciated by those skilled in
the art, many power circuits require that such mutual energization may be
avoided, and the interlocks enable a simple mechanism to maintain the
current-carrying path open through one device while it is closed through
one another. A currently contemplated design for the interlock as
illustrated in FIGS. 23 and 24. The interlock may include a housing 200
that is generally symmetrical about a vertical center line allowing for
reduction in parts because only a front and a back of the housing are
required. The housing may be structured to be easily mounted between
adjacent module switching devices. The housing may include a window
opening 202 on both sides through which an actuating element 204 is
accessible. The element 204 interfaces mechanically with the side
auxiliary actuators of the switching devices described above (see, e.g.,
FIG. 7). As best illustrated in FIG. 24. A current design for the
interlock includes self-similar lever arms 206 and 208 that are mounted
pivotally within the housing. Pivot pins 210 and 212 enable pivotal
movement of the lever arms 206 and 208. These may be integrally formed
with the housing, or may be defined by separate components (e.g., roll
pins) inserted in the housing. Each lever arm carries a respective
actuating element 204, with one element extending on one side of the
structure and the other element extending on an opposite side. Each lever
arm includes an integral cam arrangement 214 and 216 that contact one
another to prevent one of the lever arms from moving to a downward
position when the other lever arm is already in a downward position.
Thus, when connected to the side auxiliary actuators of two modular
switching devices that are mounted side-by-side, only one of the
actuating elements 204 is allowed to a lower position at a time. When the
energized and shifted switching device is de-energized and shifted to an
open position then, interference between the integral cams is eliminated
and one or the other device is then free to shift to its energized or
closed position. Many advantages may flow from the interlock arrangement
illustrated, particularly the simplicity of the structure, the reduction
in the number of parts, the ability to fabricate the parts from
easily-molded materials (typically non-conductive plastics) and the ease
of manufacture. In the illustrated embodiment, as noted above, the
housing may comprise two self-similar housing shelves, while the lever
arms 206 and 208 may also be identical, as may the actuating elements
204.

Operation of a Single-Pole Switching Device

[0167] Referring to FIG. 25, based on the above described switching device
(e.g., single-pole, single current-carrying path switching device),
designated in this figure by reference numeral 218, operation (e.g.,
opening and closing) of the switching device 218 is based on controlling
electric power supplied to the operating coil 220. To control operation
of the single-pole, single current-carrying path switching device 218, as
well as any other switching device with an operating coil, an operating
coil driver circuitry 222 may be utilized. To simplify discussion, the
operating coil driver circuitry 222 will be described in relation to the
single-pole, single current-carrying path switching device 218 described
above. As depicted, the operating coil driver circuitry 222 includes a
processor 224, memory 226, an SR flip-flop 228, a comparator 230, a
switch 232, and a flyback diode 234. More specifically, as will be
described in more detail below, the memory 226 may be a tangible
non-transitory medium that stores computer-readable instructions that
when executed perform various processes described. Accordingly, in some
embodiments, the processor 224 and memory 226 may be included in the
automation controller 44 or control and monitoring circuitry 18. It
should be noted that although the SR flip-flop 228 and the comparator 230
are described as discrete hardware components, in other embodiments, they
may be implemented by the processor 224 as computer readable
instructions.

[0168] As will be described in more detail below, the operating coil
driver circuitry 222 controls operation of the switching device 218 by
controlling the current in the operating coil (i.e., Icoil). In the
depicted embodiment, the operating coil current may be determined by
measuring the voltage at node 236 (i.e., Vnode). More specifically, since
the operating coil current flows through resistor 238 to ground, the
operating coil current is equal to the voltage at node 236 divided by the
resistance of the resistor 238. As such, the resistor 238 is generally
referred to as a current measuring resistor. In other words, the voltage
at node 236 may be used as a proxy for the operating coil current.

[0169] Additionally, as depicted, the node voltage is applied to the
non-inverting terminal of the comparator 230 and compared to a reference
voltage (i.e., Vref), which is applied to the inverting terminal of the
comparator 230. More specifically, the processor 224 outputs a voltage
that is smoothed into the DC reference voltage by resistor 240 and
capacitor 242, which corresponds with the voltage expected to be measured
at node 236 when the target (e.g., desired) operating coil current flows
through resistor 238. In other embodiments, the processor 224 may include
a digital-to-analog (DAC), thereby obviating the resistor 240 and the
capacitor 242. In this manner, the reference voltage may be equal to the
target operating coil current multiplied by the resistance of resistor
238.

[0170] Accordingly, when the node voltage is higher than the reference
voltage, the output of the comparator 230 is high indicating that the
operating coil current is higher than the target. On the other hand, when
the node voltage is lower than the reference voltage, the output of the
comparator 230 is low indicating that the operating coil current is lower
than the target. In other words, the processor 224 may indicate the
target operating coil current with the reference voltage.

[0171] The result of the comparison performed by the comparator 230 is
applied to the R terminal of the SR flip-flop 228. At the S terminal of
the SR flip-flop 228, the processor applies a trigger signal 244, which
periodically goes high to set the SR flip-flop 228. Based on the result
of the voltage comparison and the trigger signal 244, the SR flip-flop
228 outputs a pulse-width-modulated (PWM) signal to the switch 232 and
the processor 224. More specifically, the PWM signal is low when the
input from the comparator 230 is high, thereby instructing the switch to
turn off and disconnect electric power from the operating coil 220. On
the other hand, the PWM signal goes high when the input from comparator
230 is low and the trigger signal 244 is high, thereby instructing the
switch 232 to turn on and supply electric power from the power supply 246
to the operating coil 220.

[0172] In this manner, the trigger signal 244 is input to the SR flip-flop
228 to facilitate generating the PWM signal by periodically attempting to
turn on the switch 232. In some embodiments the frequency of the trigger
signal 244 may be based at least in part on desired resolution, how
quickly current decays in the coil 220, and/or line frequency of the
power supply 246. For example, when the line frequency is 60 Hz, the
trigger signal may have a frequency of 21.6 kHz (i.e., 1/(60*360)) to
achieve a one electrical degree resolution.

[0173] Based on the PWM signal, the switch 232 selectively connects or
disconnects the operating coil 220 from electric power supplied by the
power supply 246 to a DC bus 248. More specifically, the power supply 246
may output DC electric power to the DC bus 248 based on an external AC or
DC power source, such as power source 12. In some embodiments, the power
supply 246 may store some electric power to decouple the operating coil
control circuitry 222 from the power source. For example, decoupling may
reduce the effect of variations in the power source, such as a brown out,
on the operation of the operating coil control circuitry 222.

[0174] As described above, when the PWM signal is high, the switch 232
connects the operating coil 220 to the DC bus 248 to supply electric
power to the operating coil 220. On the other hand, when the PWM signal
is low, the switch 232 disconnects the operating coil 220 from the DC bus
248 to remove electric power from the operating coil 220. In this manner,
the PWM signal may control the duration the electric power is connected
and, thus, the operating coil voltage.

[0175] More specifically, the operating coil voltage may be equal to the
DC bus voltage when the switch 232 is on and equal to voltage across the
flyback diode 234 when the switch 232 is off. As such, the average
operating coil voltage (i.e., voltage drop across the operating coil 220)
may approximately equal to the DC bus voltage times the PWM signal duty
cycle. Since the operating coil current is directly related to the
operating coil voltage, the operating coil current may also be controlled
by adjusting the duty cycle of the PWM signal. For example, when duty
cycle is increased, the operating coil current increases and, when the
duty cycle is decreased, the operating coil current decreases.

[0176] Accordingly, aside from providing the reference voltage and the
trigger signal 244, the operating coil current may be adjusted to the
target coil current relatively independent from the processor 224. For
example, when the operating coil current is lower than the target, the SR
flip-flop 228 outputs the PWM signal to instruct the switch 232 to
connect electric power from the power supply 34 to the operating coil
220. On the other hand, when the comparator 230 determines that the
operating coil current is higher than the target, the SR flip-flop 228
outputs the PWM signal to instruct the switch 232 to disconnect the power
supply 246 from the operating coil 220.

[0177] In this manner, the operating coil current may be regulated
relatively independent from the processor 224. Nevertheless, the
processor 224 may still receive the PWM signal from the SR flip-flop 228.
As will be described in more detail below, the PWM signal may enable the
processor 224 to determine when the switching device 218 makes or breaks,
as well as other diagnostic information.

[0178] As described above, the operating coil driver circuitry 222 may
control operation of the switching device 218 by controlling the
operating coil current. For example, to make (i.e., close) the switching
device 218, the operating coil driver circuitry 222 may supply electric
power to the operating coil 220, which magnetizes the operating coil 220.
The magnetized operating coil 220 then attracts the armature 118, one
embodiment of which is depicted in FIG. 8, to close the switching device
218. To help illustrate, a profile of the operating coil current 250 used
to make the switching device 218 is shown in FIGS. 26A and 26B, which is
a zoomed in view of FIG. 26A.

[0179] As depicted in FIG. 26A, between t0 and t1, current is not supplied
to the operating coil 220. At t1, a small amount of current insufficient
to close the switching device 218 is supplied to the operating coil 220.
More specifically, as will be described in more detail below, the small
amount of current may be utilized to measure the temperature (e.g.,
actual or relative temperature) of the operating coil 220. Accordingly,
the operating coil current 250 between t1 and t2 is generally referred to
herein as the "measurement current." Moreover, the measurement current
may also serve to "precharge" the magnetic flux in the operating coil
220, thereby reducing amount of current increase to close the switching
device. In this manner, repeatability and/or timing of closing the
switching device 218 may be further improved.

[0180] Between t2 to t3, the operating coil current 250 is ramped up from
the measurement current to a level sufficient to close the switching
device 218. Accordingly, the operating coil current 250 between t3 and t4
is generally referred to herein as the "pull-in current." It should be
noted that as in the depicted embodiment, the current is partially ramped
up to an intermediate current level between the measurement current and
the pull-in current. In some embodiments, the operating coil driver
circuitry 222 may ramp the current to the intermediate current level to
further precharge the magnetic flux in the operating coil 220, thereby
reducing amount of current increase to close the switching device.
Additionally or alternatively, the current may be directly ramped up from
the measurement current to the pull-in current.

[0181] Upon ramping the operating coil current 250 up to the pull-in
current, the armature 118 may begin to move. As the armature 118 moves,
the impedance of the operating coil 220 increases. More specifically, the
armature 118 may behave as both a position variable inductor and as a
linear motor and, thus, affect inductance (e.g., impedance) of the
operating coil 220 when in motion. Accordingly, to maintain the operating
coil current 250 at the target level (e.g., pull-in current), the
operating coil driver circuitry 222 may increase the amount of electric
power supplied to the operating coil 220. As described above, this may
include increasing the duty cycle of the PWM signal.

[0182] By design, at t4, the impedance of the operating coil 220 has
increased to a point where the electric power supplied by the power
supply 246 is no longer able to maintain the operating coil current 250
at the pull-in current. As depicted, the operating coil current 250
sharply drops. After the switching device 218 makes, the impedance of the
operating coil 220 returns to normal, thereby enabling the operating coil
current 250 to return to the pull-in current. More specifically, when the
armature 118 stops moving (e.g., when it hits the yoke 106) inductance
generated by movement of the armature may dissipate. Accordingly, as
depicted, the operating coil current 250 returns to the pull-in current
at t5, which produces a "V" between t4 and t5.

[0183] In fact, as will be described in more detail below, the profile of
the operating coil current 250 (e.g., duration between t4 and t5) may be
used as an indication of armature 118 position and, thus, when the
switching device 218 makes. More specifically, at some time between t4
and t5, for example at tM, the switching device 218 makes. The drop in
the operating coil current 250 between t4 and t5 is more clearly depicted
in FIG. 26B.

[0184] As depicted, after t5, the operating coil current 250 is reduced to
a current level sufficient to hold the switching device 218 closed. As
such, the operating coil current 250 after t5 is generally referred to
herein as the "hold-in current." In some embodiments, the operating coil
current 250 may be reduced to the hold-in current to reduce the power
consumption of the switching device 218 and/or ohmic heating of the
operating coil 220.

[0185] Based on the above description, the make time of the switching
device 218 is generally not instantaneous. As used herein, the "make
time" is generally intended to describe the time between when pull-in
current is applied and when the switching device 218 makes. For example,
there is a slight delay between when pull-in current is applied at t3 and
when the switching device 218 actually makes at tM. Accordingly, the
operating coil driver circuitry 222 may take into account the
non-instantaneous nature of the switching device 218 to improve control
of the switching device 218, for example, to facilitate making the
switching device 218 at a specific point on the electric power waveform.
To help illustrate, FIG. 27 depicts a source voltage waveform 252 of one
phase of electric power supplied to the switching device 218 from the
power source 12.

[0186] As described above, to reduce magnitude of inrush current and/or
current oscillation, the switching device 218 may be closed based upon a
predicted current zero-crossing (e.g., a point on source waveform 252
within a range from slightly before to slightly after the predicted
current zero-crossing). As described above, the predicted current
zero-crossing may occur at a line-to-line voltage maximum (e.g.,
90.degree. after a line-to-line voltage zero crossing or 60.degree. after
a line-to-neutral voltage zero crossing). For example, in the depicted
embodiment, the switching device 218 is desired to make at point 254
(e.g., a line-to-line voltage maximum). As described above, the switching
device 218 may be closed by setting the operating coil current 250 to the
pull-in current to attract the armature 118. Accordingly, since the
switching device 218 generally does not make instantaneously, the
operating coil current 250 may be set to the pull-in current at an
earlier time to make the switching device 218 at a tM that corresponds
with the point 254.

[0187] More specifically, the operating coil current 250 may be controlled
based at least in part on the expected make time of the switching device
218. Based on the above described example, the operating coil current 250
is set to the pull-in current at t3 to make the switching device 218 at
tM. In other words, the expected make time 256 of the switching device is
the difference between t3 and tM. The operating coil current 250 may then
be controlled based at least in part on the expected make time 256 of the
switching device 218 (e.g., difference between t3 and tM).

[0188] One embodiment of a process 258 that may be used to make the
switching device 218 at a specific point on an electric power waveform is
shown in FIG. 28. The process 258 may be implemented via
computer-readable instructions stored in the tangible non-transitory
memory 226, 20, 46, and/or other memories and executed via processor 224,
19, 45, and/or other control circuitry. Generally, the process 258
includes determining a desired time to make the switching device 218
(process block 260), determining an expected make time of the switching
device 218 (process block 262), and applying the current profile to make
the switching device 218 at the desired time (process block 264).
Additionally, the process 258 optionally includes determining when the
switching device 218 makes (process block 266).

[0189] In some embodiments, the processor 224 may determine the desired
time to make the switching device 218 (process block 260). As described
above, the switching device 218 may be closed a specific point on the
electric power waveform to minimize in-rush current, current transients,
current oscillations and/or torque oscillations. Accordingly, in some
embodiments, the processor 224 may determine that the specific point
corresponds to a predicted current zero-crossing and/or a line-to-line
voltage maximum. The processor 224 may then determine the time associated
with the specific point.

[0190] As can be appreciated, each step in process 258 is generally not
instantaneous. Accordingly, the desired time to make the switching device
218 may be selected to provide sufficient time to complete process 258.
In other words, the desired time to make may not always correspond with
the first subsequent predicted current zero-crossing. Additionally, in
some embodiments, a user may instruct the operating coil driver circuitry
222 to close the switching device 218 as soon as possible independent of
the electric power waveform and the processor 224 may determine the
desired time to make accordingly.

[0191] The processor 224 may then determine the expected make time 256 of
the switching device 218 (process block 262). The make time of the
switching device 218 may be affected by various operational parameters,
such as temperature. As will be described in more detail below, the
temperature (e.g., actual temperature or relative temperature) may be
determined via impedance of the operating coil 220 or other methods, such
as a temperature sensor. Accordingly, the processor 224 may determine the
various operational parameters, for example via sensors 22 or the
measurement current, to determine the expected make time 256 of the
switching device 218.

[0192] More specifically, in some embodiments, the processor 224 may input
the operational parameters into a make time look-up-table (LUT) that
relates the determined operational parameters to an expected make time
256. For example, when a specific temperature is input to the make time
LUT, the LUT may output an expected make time 256. Although the described
embodiments describe the used of look-up tables (LUTs), in other
embodiments, the same results may be achieved by calculations performed
by the processor 224 using various algorithms or a combination of
algorithms and LUTs. Additionally, since the make time LUT, may be
determined during normal operations, the processor 224 may adjust for any
other known operational parameters that may affect the expected make time
256, such as a filtering delay, device wear, and/or other environmental
conditions.

[0193] In some embodiments, the make time LUT may be based on empirical
tests, such as past make times. For example, in some embodiments, a
manufacturer may conduct tests on the particular switching device 218 or
a comparable switching device 218 to determine the make time of the
switching device 218 under the various operational parameters and
populate the make time LUT accordingly. Additionally, when the switching
device 218 is put into commission, the switching device 218 may run a
testing sequence to determine when the switching device 218 makes under
the various sets of operational parameters to calibrate the make time
LUT.

[0194] Since the techniques described herein are based on previous
operations, it is emphasized that the single-pole, single
current-carrying path switching device 218 described above is designed to
have highly repeatable and, thus, highly predictable operation. As such,
the make time LUT enables the processor 224 to determine, with a
reasonable certainty, the make time of the switching device 218 based on
the make time of the switching device 218 previously under similar
parameters. Nevertheless, it should be appreciated that the techniques
may also be used for other types of switching devices, such as a
multi-pole switching device.

[0195] Based on the expected make time, the current profile may be applied
to the switching device 218 to make the switching device 218 at the
determined time (process block 264). For example, the current profile may
set the operating coil current 250 to the pull-in current. More
specifically, the processor 224 may determine when to apply the current
profile to the switching device 218 to make at the desired time. In some
embodiments, the processor 224 may determine a specific time to apply the
current profile by subtracting the expected make time 256 from the
desired time to make. For example, subtracting the expected make time 256
from tM (e.g., desired time to make) results in t3 (e.g., the specific
time to apply the current profile). Accordingly, as described above, the
current profile is applied to the switching device 218 at t3.

[0196] Additionally, as described above, the operating coil current 250
may be ramped up to an intermediate level before the pull-in current.
Accordingly, in such embodiments, the processor 224 may determine when to
ramp up to the intermediate level. For example, the processor 224 may
determine a specific time to ramp up to the intermediate level by
subtracting a ramp up period (e.g., time between t2 and t3) from t3.

[0197] After the current profile is applied, the processor 224 may
optionally determine when the switching device 218 makes (process block
266). More specifically, determining when the switching device 218 makes
may enable determining the actual make time of the switching device 218.

[0198] As described above, the make time LUT may be based at least in part
on past make operations. However, the make time of the switching device
218 may gradually change over time. For example, as the switching device
218 ages, the force provided by the spring 110 that resists closing the
switching device 218 may gradually decrease, which may gradually reduce
the make time of the switching device 218. Additionally, as contact
material wears away, the distance the switching device 218 moves to close
may increase and/or debris may building up causing friction, which may
gradually increase the make time of the switching device 218.

[0199] Accordingly, determining the actual make time may facilitate
calibrating and/or updating the make time LUT to better account for
operational changes in the switching device. In fact, as will be
described in more detail below, keeping track of the actual make times
may facilitate performing diagnostics on the switching device 218. For
example, if the make time of the switching device 218 is different than
expected, the processor 224 may identify that the switching device 218
may be obstructed in some way or suffering from some other anomalous
condition.

[0200] In some embodiments, the processor 224 may utilize the PWM signal
to determine when the switching device 218 makes. More specifically, as
described above, the PWM signal output by the SR flip-flop 228 is fed
back to the processor 224. Based on the duty cycle of the PWM signal, the
processor 224 may determine duration of the drop in the operating coil
current (e.g., duration between t4 and t5), which may be directly related
to when the switching device 218 makes.

[0201] To help illustrate, FIG. 29 depicts the trigger signal 244 output
by the processor 224 and the PWM signal 268 input to the processor 224.
As described above, the trigger signal 244 is input to the SR flip-flop
228 to facilitate generating the PWM signal 268 by periodically
attempting to set the SR flip-flop 228 (e.g., make the PWM signal 268
high). More specifically, when comparator 230 determines that the
operating coil current 250 is lower than the target and the trigger
signal 244 is high, the SR flop-lop 228 outputs a high PWM signal 268
instructing the switch to turn on, thereby supply electric power from the
power supply 246 to the operating coil 220. On the other hand, when the
comparator 230 determines that the operating coil 250 is not lower than
the target, the SR flop-lop 228 outputs a low PWM signal 268 instructing
the switch to turn off, thereby disconnecting electric power from the
operating coil 220. In other words, the PWM signal 268 may turn on the
switch 232 and the switch 232 may remain on until the comparator 230
determines that the operating coil current 250 is greater than the
reference voltage (i.e., Vref). At that point, the comparator 230 may
reset the SR flip-flop 282, thereby turning off the switch 232.

[0202] As described above, between t3 and t4, the operating coil current
250 is set at the pull-in current. Accordingly, in the depicted
embodiment, supplying electric power to the operating coil 220 based on
the PWM signal 268 depicted between t3 and t4 may maintain the operating
coil current 250 at the pull-in current. Additionally, as described
above, after the armature 118 begins to move, the impedance of the
operating coil 220 begins to increase. Accordingly, as depicted, the duty
cycle of the PWM signal 268 gradually increases between t3 and t4 to
compensate for the impedance increase and maintain the operating coil
current 250 at the pull-in current.

[0203] In other words, the SR flip-flop 228 may continue to increase the
duty cycle of the PWM signal 268 in an attempt to maintain the operating
coil current 250 at the pull-in current. Accordingly, the sharp drop in
operating coil current 250 between t4 and t5, described above, indicates
that even the maximum electric power output by the power supply 246 is
insufficient to maintain the operating coil current 250 at the pull-in
current. Thus, as depicted, the duty cycle of the PWM signal 268 is
increased to 100% between t4 and t5. As such, the processor 224 may
determine the duration between t4 and t5 by determining duration the PWM
signal 268 is at 100% duty cycle.

[0204] Accordingly, as will be described in more detail below, the power
supply 246, the magnitude of the pull-in current, and/or the coil design
may be determined to produce the sharp operating coil drop between t4 and
t5. It should be noted that 100% duty cycle is merely intended to be
illustrative. In other embodiments, the processor 224 may determine the
make time and/or when the switching device makes by determining duration
duty cycle of the PWM signal 268 is at another predetermined level.

[0205] As described above, the duration between t4 and t5 (e.g., when the
PWM signal 268 is at 100% duty cycle) may be utilized to determine when
the switching device 218 makes. One embodiment of a process 270 to
determine when the switching device 218 makes is shown in FIG. 30. The
process 270 may be implemented via computer-readable instructions stored
in the tangible non-transitory memory 226, 20, 46 and/or other memories
and executed via processor 224, 19, 45 and/or other control circuitry.
Generally, the process 270 includes determining when the PWM signal
reaches 100% duty cycle (process block 272), determining when the PWM
signal duty cycle falls below 100% (process block 274), determining the
duration the PWM signal is at 100% duty cycle (process block 276),
determining when the switching device makes (process block 278), and
updating the LUT with the determined make time (process block 280).

[0206] In some embodiments, the processor 224 may determine when the duty
cycle of the PWM signal 268 reaches 100% (process block 272). As
described above, the duty cycle reaching 100% may indicate that the
maximum amount of electric power is being supplied to the operating coil
220, which corresponds with when the operating coil current 250 begins to
drop (e.g., at t4). Additionally, the processor 224 may determine when
the duty cycle of the PWM signal 268 falls below 100% (process block
274). As described above, the duty cycle falling below 100% may indicate
that the armature 119 is no longer moving and the switching device 218 is
closed, which correspond with when the operating coil current 250 returns
to the pull-in current (e.g., at t5). Accordingly, based on when the duty
cycle reaches 100% and when the duty cycle falls below 100%, the
processor 224 may determine the duration the duty cycle of the PWM signal
268 remains at 100%, which may indicate duration of the drop in the
operating coil current 250 (e.g., duration between t4 and t5) (process
block 276).

[0207] Based on the duration the duty cycle is at 100%, the processor 224
may determine when the switching device 218 makes (process block 278).
More specifically, a relationship between tM and the duration between t4
and t5 may be defined based on empirical testing (e.g., historical data).
In some embodiments, the historical data may define that tM occurs at a
certain percentage between t4 and t5. For example, the historical data
may define that tM occurs at a time 30% between t4 and t5. In fact, in
some embodiments, the switching device 218 may be periodically
recalibrated to determine the relationship between tM and the duration
between t4 and t5, for example, using a high speed camera and/or current
sensors.

[0208] Similar to the make time LUT, a manufacturer of the switching
device 218 may conduct tests on the particular switching device 218 or a
comparable switching device 218 to determine when tM occurs in relation
to the duration of t4 to t5. Additionally, it is again emphasized that
the single-pole, single current-carrying path switching device 218
described above is designed to have a highly repeatable and, thus, highly
predictable, operation. In other words, the defined relationship between
tM and the duration of t4 to t5 enables the processor 224 to determine,
with a reasonable certainty, when the switching device 218 makes.

[0209] Additionally or alternatively, when the switching device 218 makes
may be verified by measuring when current begins to flow through the
switching device 218. For example, a sensor 22 may be placed between the
switching device 218 and the load to feed back a signal indicating that a
current is flowing. Thus, the processor 224 or other control circuitry
may verify when the switching device 218 makes. Other techniques, such as
high speed cameras, auxiliary contacts, optical or magnetic position
sensors, and/or flux detectors, may also be used to verify when the
switching device 218 makes.

[0210] Furthermore, in some embodiments, the instant the switching device
218 closes may be determined based at least in part on other
characteristics the operating coil current 250, such as an inflection in
the current waveform. More specifically, when the switching device 218
closes, the biasing spring 152 may be added to the load seen by the
armature 118 (e.g., magnetic system), thereby causing the armature 118 to
slow down and causing an inflection in the operating coil current 250. In
some embodiments, the verification may be performed at a later time and
used to calibrate the make time LUT.

[0211] The processor 224 may then update the make time LUT with the
determined make time (process block 280). More specifically, the
processor 224 may determine the make time based on the time difference
between when the pull-in current is applied (e.g., at t3) and when the
switching device makes (e.g., at tM). As described above, updating the
make time LUT with the determined make time may enable the operating coil
driver circuitry 222 to compensate for operational changes in the
switching device 218 as well as perform diagnostics on the switching
device 218.

[0212] In addition to controlling the make operation of the switching
device 218, the operating coil driver circuitry 222 may be used to
control the break (i.e., open) operation of the switching device 218. For
example, to break the switching device 218, the operating coil driver
circuitry 222 may reduce electric power to the operating coil 220, which
reduces the magnetic force generated by the operating coil 220 to hold
the switching device 218 closed. Accordingly, the spring 110 may overcome
the magnetic force generated by the operating coil 220 and open the
switching device 218. To help illustrate, the operating coil current 250
and the target operating coil current 282 to break the switching device
218 are shown in FIG. 31.

[0213] As depicted in FIG. 31, before t6, the operating coil current 250
is generally set at the target operating coil current 282. More
specifically, as described above, the operating coil driver circuitry 222
may adjust the operating coil current 250 by connecting and disconnecting
electric power supplied from the power supply 246 from the operating coil
220. In some embodiments, the operating coil current 250 may be set at
the hold-in current.

[0214] At t6, the target operating coil current 282 is reduced to a level
insufficient to hold the switching device 218 closed. As will be
described in more detail below, the target operating coil current 282
after t6 may be utilized to determine when the switching device 218
breaks. Accordingly, the target operating coil current after t6 is
generally referred to herein as the "break current." Initially when the
target operating coil current is reduced to the break current at t6, the
operating coil current 250 is higher than the target and electric power
is disconnected from the operating coil 220. More specifically, as
depicted, the operating coil current 250 gradually decreases as the
operating coil 220 dissipates energy stored in its magnetic field via the
flyback diode 234. In other embodiments, the flyback diode 234 may be
connected between resistor 238 and ground. Additionally, in other
embodiments, the flyback diode 234 may be replaced with an active device,
such as a field effect transistor (FET).

[0215] As the operating coil current 250 continues to decrease, the
magnetic force produced by the operating coil 220 will no longer be
sufficient to hold the switching device 218 closed, thereby causing the
switching device 218 to begins to move (e.g., open). Additionally, the
collapse of the magnetic field collapses may generate (e.g., induce) a
current in the operating coil 220 due to back electromotive force (EMF).
More specifically, the back EMF may be caused by the line of flux being
dragged along the armature 118 and the coil windings 112 as the switching
device 218 opens. Accordingly, when the switching device 218 breaks may
be determined by detecting when the current is generated in the operating
coil 220.

[0216] As described above, the operating coil current 250 may gradually
decrease as the operating coil 220 dissipates the energy stored in its
magnetic field. In other words, if electric power is not reconnected to
the operating coil 220, the generated current may be determined by
identifying the minimum in the operating coil current 250. As depicted,
the operating coil current 250 is maintained at the target operating coil
current 282 between t7 and t8. Accordingly, the minimum operating coil
current 250 is at some time between t7 and t8. In other words, the
switching device 218 breaks at some time between t7 and t8, for example
at tB. Thus, similar to determining when the switching device 218 makes
the duration between t7 and t8 may be used with historical data and/or
design attributes of the switching device 218 to determine when the
switching device 218 breaks (e.g., at tB).

[0217] As depicted, at t8, the generated current in the operating coil 220
causes the operating coil current 250 to increase above the target
operating coil current 282 (e.g., break current). In other words, even
though the power supply 246 is disconnected from the operating coil 220,
the operating coil current 250 rises above the target operating coil
current 282. Accordingly, to facilitate determining the duration between
t7 and t8, the break current is set slightly below the current induced in
the operating coil 220 by the movement of the armature 118. Additionally,
as depicted, after t9, the operating coil current 250 is maintained at
the break current.

[0218] Similar to the make time, based on the above description, the break
time of the switching device 218 is generally not instantaneous. In other
words, there is a slight delay between when the target operating coil
current 282 is reduced to the break current (e.g., at t6) and when the
switching device 218 actually breaks (e.g., at tB). As used herein, the
"break time" is generally intended to describe that time period.
Accordingly, the operating coil driver circuitry 222 may take into
account the non-instantaneous nature of the switching device 218 to
improve control of the switching device 218, for example, to break the
switching device 218 at a specific point on the electric power waveform.
To help illustrate, FIG. 32 depicts a switching device current waveform
284 of electric power conducted by the switching device 218.

[0219] As described above, to reduce electrical arcing, the switching
device 218 may be opened based upon a current zero-crossing (e.g., a
point on the switching device current waveform 284 within a range from
slightly before to the current zero-crossing). For example, in the
depicted embodiment, the switching device 218 is desired to break at a
current zero-crossing at point 286. As described above, the switching
device 218 may be opened by setting the operating coil current 250 to the
break current to enable the spring 110 to overpower the magnetic force
generated by the operating coil 220. Accordingly, since the switching
device 218 generally does not break instantaneously, the operating coil
current 250 may be set to the break current at an earlier time to break
the switching device 218 at tB, which corresponds with the point 286.

[0220] More specifically, the operating coil current 250 may be controlled
based at least in part on the expected break time of the switching device
218. Based on the above described example, the target operating coil
current 282 is set to the break current at t6 to break the switching
device 218 at tB. In other words, the expected break time 288 of the
switching device is the difference between t6 and tB.

[0221] One embodiment of a process 290 that may be used to break the
switching device 218 at a specific point on an electric power waveform is
shown in FIG. 33. The process 290 may be implemented via
computer-readable instructions stored in the tangible non-transitory
memory 226, 20, 46 and/or other memories and executed via processor 224,
19, 45 and/or other control circuitry. Generally, the process 290
includes determining a desired time to break the switching device 218
(process block 292), determining an expected break time of the switching
device 218 (process block 294), and applying the current profile to break
the switching device 218 at the desired time (process block 296).
Additionally, the process 290 optionally includes determining when the
switching device 218 breaks (process block 298).

[0222] In some embodiments, the processor 224 may determine the desired
time to break the switching device (process block 292). As described
above, the switching device 218 may be opened based on a current-zero
crossing of the conducted electric power. Additionally, the processor 224
may determine the time associated with the specific point. Accordingly,
in some embodiments, the processor 224 may determine the desired time to
break the switching device 218 based on a subsequent current
zero-crossing.

[0223] As can be appreciated, each step in process 290 may generally be
non-instantaneous. Accordingly, in some embodiments, the desired time to
break the switching device 218 may be selected to provide sufficient time
to complete process 290. In other words, the desired time may not always
correspond with the first subsequent zero-crossing. In other embodiments,
it may be desired to break the switching device 218 as soon as possible
independent of the electric power waveform and the processor 224 may
determine the desired time to break accordingly.

[0224] The processor 224 may then determine the expected break time 288 of
the switching device 218 (process block 294). Similar to the make time,
the break time of the switching device 218 may be affected by various
operational parameters, such as temperature, wear, fatigue, and/or
debris. As will be described in more detail below, the temperature (e.g.,
actual temperature or relative temperature) may be determined via
impedance of the operating coil 220 or other methods, such as a
temperature sensor. Accordingly, the processor 224 may determine the
various operational parameters, for example via sensors 22 or the hold-in
current, to determine the expected make time 256 of the switching device
218.

[0225] More specifically, the processor 224 may input the operational
parameters into a break time look-up-table (LUT) that relates the
determined operational parameters to an expected break time 288. For
example, when a specific temperature is input to the break time LUT, the
LUT may output an expected break time 288. Additionally, the processor
224 may adjust for any other known offsets that may affect the expected
break time 288, such as a filtering delay. Although the described
embodiments describe the used of look-up tables (LUTs), in other
embodiments, the same results may be achieved by calculations performed
by the processor 224 using various algorithms or a combination of
algorithms and LUTs. Additionally, since the break time LUT, may be
determined during normal operations, the processor 224 may adjust for any
other known operational parameters that may affect the expected make time
256, such as a filtering delay, device wear, and/or other environmental
conditions.

[0226] Similar to the make time LUT, the break time LUT used to determine
expected break time may be based on empirical tests, such as past break
times. For example, in some embodiments, a manufacturer may conduct tests
on the particular switching device 218 or a comparable switching device
218 to determine the break time of the switching device 218 under the
various operational parameters and populate the break time LUT
accordingly. Additionally, when the switching device 218 is put into
commission, the switching device 218 may run a testing sequence to
determine when the switching device 218 breaks under the present
parameters and calibrate the break time LUT.

[0227] Since the techniques described herein are based on previous
operations, it is again emphasized that the single-pole, single
current-carrying path switching device 218 described above is designed
having a highly repeatable and thus highly predictable operation. In
other words, the break time LUT enables the processor 224 to determine,
with a reasonable certainty, the break time of the switching device 218
based on the break time of the switching device 218 previously under
similar parameters. Nevertheless, it should be appreciated that the
techniques may also be used for other types of switching devices, such as
a multi-pole switching device.

[0228] Based on the expected break time, the current profile may be
applied to the switching device 218 to break the switching device 218 at
a determined time (process block 296). More specifically, the processor
224 may determine when to apply the current profile to the switching
device 218 to break at the desired time. In some embodiments, the
processor 224 may determine a specific time to apply the current profile
by subtracting the expected break time 288 from the desired time to make.
For example, subtracting the expected break time 288 from tB (e.g.,
desired time to make) results in t6 (e.g., the specific time to apply the
current profile). Accordingly, as described above, the target operating
coil current 282 is set at the hold-in current (e.g., current profile) at
t6. It should be noted that it may be desirable to break the switching
device 218 slightly before the current zero-crossing to minimize the
chances of breaking after the zero-crossing.

[0229] After the current profile is applied, the processor 224 may
optionally determine when the switching device 218 breaks (process block
298). More specifically, determining when the switching device 218 makes
may enable determining the actual make time of the switching device 218.

[0230] As described above, the break time LUT may be based at least in
part on past break operations. However, the break time of the switching
device 218 may gradually change over time. For example, as the switching
device 218 ages, the force provided by the spring 110 that opens the
switching device 218 may gradually decrease, which may gradually increase
the break time of the switching device 218. Additionally, as contact
material wears away, the distance the switching device 218 moves to open
may increase and/or debris may build up causing friction, which may
gradually increase the break time of the switching device 218.

[0231] Accordingly, determining the actual break time may facilitate
calibrating and/or updating the break time LUT to better account for
operational changes in the switching device. In fact, as will be
described in more detail below, keeping track of the actual break times
may facilitate performing diagnostics on the switching device 218. For
example, if the break time of the switching device 218 is different than
expected, the processor 224 may identify that the switching device 218
may be obstructed in some way or suffering from some other anomalous
condition.

[0232] In some embodiments, the processor 224 may utilize the PWM signal
to determine when the switching device 218 makes. More specifically, as
described above, the PWM signal output by the SR flip-flop 228 is fed
back to the processor 224. Based on the duty cycle of the PWM signal, the
processor 224 may determine in duration the operating coil current is
below the break current (e.g., duration between t4 and t5), which may be
directly related to when the switching device 218 breaks.

[0233] To help illustrate, FIGS. 34A and 34B depicts the trigger signal
244 output by the processor 224 and the PWM signal input 268 to the
processor 224. More specifically, FIG. 34A depicts the PWM signal 268
output by a standard SR flip-flop and FIG. 34B depicts the PWM signal 268
output by an SR flip-flop that is set each time the S terminal goes high.

[0234] As described above, the trigger signal 244 is input to the SR
flip-flop 228 to facilitate generating the PWM signal 268 by periodically
attempting to set the SR flip-flop 228 (e.g., make the PWM signal 268
high). More specifically, when comparator 230 determines that the
operating coil current 250 is lower than the target and the trigger
signal 244 is high, the SR flop-lop 228 outputs a high PWM signal 268
instructing the switch to turn on, thereby supply electric power from the
power supply 246 to the operating coil 220. On the other hand, when the
comparator 230 determines that the operating coil current 250 is not
lower than the target, the SR flop-lop 228 outputs a low PWM signal 268
instructing the switch to turn off, thereby disconnecting electric power
from the operating coil 220. In other words, the trigger signal 244 may
turn on the switch 232 and the switch 232 may remain on until the
comparator 230 determines that the operating coil current 250 is greater
than the reference voltage (i.e., Vref). At that point, the comparator
230 may reset the SR flip-flop 282, thereby turning off the switch 232.

[0235] As described above, between t6 and t7, the operating coil current
250 is higher than the target operating coil current 282. Thus, the
comparator 230 will input a high signal to the R terminal of the SR
flip-flop 228. In other words, in a standard SR flip-flop, the PWM signal
268 will be low regardless of the input at the S terminal. Accordingly,
as depicted, duty cycle of the PWM signal 268 between t6 and t7 is 0%. In
other words, the power supply 246 is disconnected from the operating coil
220 as the energy stored in the operating coil 220 is gradually
dissipated.

[0236] Additionally, as described above, the SR flip-flop 228 may increase
the duty cycle of the PWM signal 268 to maintain the operating coil
current 250 at the target operating coil current 282. Thus, when the
operating coil current 250 begins to drop below the target operating coil
current 282 between t7 and t8, electric power is supplied to the
operating coil 220 to maintain the operating coil current 250 at the
target operating coil current 282. Accordingly, in the depicted
embodiment, the PWM signal 268 has a non-zero duty cycle to maintain the
operating coil current 250 at the break current. As such, the process 224
may determine the duration between t7 and t8 by determining the duration
the PWM is at a non-zero duty cycle.

[0237] Furthermore, as described above, when the armature 118 begins to
move, a current is generated in the operating coil 220, which causes the
operating coil current 250 to rise above the target operating coil
current 282 between t8 and t9. Since the operating coil current 250 is
higher than the target operating coil current 282, electric power is
disconnected from the operating coil 220. Accordingly, as depicted, the
duty cycle of the PWM signal 268 between t8 and t9 is 0%.

[0238] Additionally, as described above, after t9, the generated current
decreases below the target operating coil current 282 and the operating
coil current 250 is maintained at the target operating coil current 282
by connecting and disconnecting electric power. Accordingly, in the
depicted embodiment, the PWM signal 268 has a non-zero duty cycle after
t9 to maintain the operating coil current 250 at the break current. Thus,
it may be determined that the armature 118 is no longer moving when the
duty cycle again goes non-zero (e.g., at t9).

[0239] The embodiment of the PWM signal 268 shown in FIG. 34B is similar
to the one shown in FIG. 34A with the distinction that the SR flip-flop
228 used to generate the PWM signal 268 shown in FIG. 34B goes high
whenever the input to the S terminal goes high. In other words, as
depicted, between t6 and t7, since the operating coil current 250 is
higher than the target operating coil current 282, the duty cycle of the
PWM signal 268 is at its minimum. In some embodiments, the minimum duty
cycle may be equal to the duty cycle of the trigger signal 244.
Accordingly, the duration between t7 and t8 may be determined by the
duration the duty cycle of the PWM signal 268 is above its minimum.

[0240] In fact, since minimum duty cycle is non-zero, the PWM signal 268
may instruct the switch 232 to turn on for at least the duty cycle of the
trigger 244. As such, a minimum amount of electric power may be supplied
to the operating coil 220. In some embodiments, supplying a positive
minimum amount of electric power to the operating coil 220 may facilitate
stabilizing oscillations in the operating coil current 250, thereby
providing a more accurate determination of the duration the operating
coil current 250 is below the break current.

[0241] Similarly, as depicted, between t8 and t9, since the operating coil
current 250 is higher than the operating current target 282 due to the
current generated by the movement of armature 118, the duty cycle of the
signal 268 is again at its minimum. More specifically, the duty cycle of
the PWM signal 268 may again be equal to the duty cycle of the trigger
signal 244. Accordingly, it may be determined that the armature 118 is no
longer moving when the duty cycle of the PWM signal 268 increases above
its minimum (e.g. after t9).

[0242] Although either embodiment of the SR flip-flop 228 may be utilized.
To simplify the following discussion, the embodiment shown in FIG. 34A
will be utilized. It should be noted that one of ordinary skill in art
will be able to easily convert between looking for a minimum duty cycle,
a 0% duty cycle, and another predetermined duty cycle.

[0243] As described above, the duration between t7 and t8 (e.g., when the
PWM signal 268 is non-zero) may be utilized to determine when the
switching device breaks. One embodiment of a process 300 is shown in FIG.
35. The process 300 may be implemented via computer-readable instructions
stored in the tangible non-transitory memory 226, 20, 46 and executed via
processor 224, 19, 45 and/or other control circuitry. Generally, the
process 300 includes determining when the PWM signal reaches 0% duty
cycle (process block 302), determine when the PWM signal duty cycle is
non-zero (process block 304), determining when the PWM signal again
reaches 0% duty cycle (process block 306), determining duration the PWM
signal duty cycle is non-zero (process block 308), determining when the
switching device breaks (process block 310), and updating the LUT with
the determined break time (process block 312).

[0244] In some embodiments, the processor 224 may determine when the duty
cycle of the PWM signal 268 reaches 0% (process block 302). As described
above, the duty cycle falling to 0% (e.g., minimum level) may indicate
that the operating coil 220 is dissipating energy stored in its magnetic
field, but still above the break current. In other words, the armature
118 has not begun to move because the minimum of the operating coil
current 250 has not yet been reached.

[0245] Additionally, the processor 224 may determine when the duty cycle
of the PWM signal 268 is non-zero (process block 304). As described
above, the duty cycle increasing to non-zero (e.g., above minimum level)
may indicate that electric power is being supplied to the operating coil
220, which corresponds with when the operating coil current 250 begins to
fall below the target operating coil current 282 (e.g., at t7).
Furthermore, the processor 224 may determine when the duty cycle of the
PWM signal 268 again goes to 0% (process block 306). As described above,
the duty cycle again falling to 0% (e.g., minimum level) may indicate
that the operating coil current 250 is higher than the target operating
coil current 282 due to the induced current in the operating coil 220
(e.g., at t8). In other words, at this point, the armature 118 is in
motion and, thus, the switching device 218 has opened at some time
between t7 and t8. Accordingly, based on when the duty cycle is non-zero
and when the duty cycle again goes to 0%, the processor 224 may determine
the duration the duty cycle of the PWM signal 268 is non-zero, which may
indicate the operating coil current 250 is below the break current (e.g.,
duration between t7 and t8) (process block 308).

[0246] Based on the duration the PWM signal is non-zero, the processor 224
may determine when the switching device 218 breaks (process block 310).
More specifically, a relationship between tB and the duration between t7
and t8 may be defined based on empirical testing (e.g., historical data).
In some embodiments, the historical data may define that tB occurs at a
certain percentage between t7 and t8. For example, the historical data
may define that tB occurs at 45% between t7 and t8. In fact, in some
embodiments, the switching device 218 may be periodically recalibrated to
determine the relationship between tB and the duration between t7 and t8,
for example, using a high speed camera and/or current sensors.

[0247] Similar to the break time LUT, a manufacturer of the switching
device 218 may conduct tests on the particular switching device 218 or a
comparable switching device 218 to determine when tB occurs in relation
to the duration between t7 to t8. Additionally, it is again emphasized
that the single-pole, single current-carrying path switching device 218
described above is designed having a highly repeatable and thus highly
predictable operation. In other words, the defined relationship between
tB and the duration of t7 to t8 enables the processor 224 to determine,
with a reasonable certainty, when the switching device 218 breaks.

[0248] Additionally or alternatively, when the switching device 218 breaks
may be verified by measuring when current ceases to flow through the
switching device 218. For example, a sensor 22 may be placed between the
switching device 218 and load to feed back a signal indicating that a
current has stopped flowing. Thus, the processor 224 or other control
circuitry may verify when the switching device 218 breaks. Other
techniques, such as a high speed camera, may also be used to verify when
the switching device 218 breaks. In some embodiments, the verification
may be performed at a later time and used to calibrate the break time
LUT.

[0249] The processor 224 may then update the break time LUT with the
determined break time (process block 312). More specifically, the
processor 224 may determine the break time based on the time difference
between when the target operating coil current 282 is set at the break
current (e.g., at t6) and when the switching device breaks (e.g., at tB).
As described above, updating the break time LUT with the determined break
time may enable the operating coil driver circuitry 222 to compensate for
operational changes in the switching device 218 as well as perform
diagnostics on the switching device 218.

[0250] In addition to utilizing the PWM signal 268, in some embodiments,
the processor 224 may determine when the switching device makes or breaks
based directly on the output of the comparator 230. More specifically, in
such embodiments, the output of comparator 230 may be input to the
processor 224, as depicted in FIG. 36.

[0251] As such, the processor 224 may determine whether the operating coil
current 250 is higher or lower than a target level based on the output of
the comparator 230. As described above, the processor 224 may output a
reference voltage (e.g., Vref) that corresponds with the target operating
coil current 282. Accordingly, the processor 224 may determine when the
operating coil current 250 is below the target operating coil current 282
when the output of the comparator 230 is low. On the other hand, the
processor 224 may determine when the operating coil current 250 is above
the target operating coil current 282 when the output of the comparator
230 is high. In fact, the processor 224 may adjust the trigger signal 224
to better handle oscillations in the operating coil current 250, for
example, by adjusting the duty cycle to adjust minimum amount of electric
power be supplied to the operating coil 220.

[0252] In fact, such an embodiment of the operating coil driver circuitry
222 may enable electric power to be completely disconnected during a
break operation. More specifically, since the processor 224 may determine
when the operating coil current 250 falls below the break current (e.g.,
duration between t7 and t8) directly from the comparator 230, the
operating coil driver circuitry 222 may allow the operating coil current
250 to dissipate naturally. In other words, the duty cycle of the PWM
signal 268 may be set to 0% to disconnect electric power from the
operating coil 220. For example, the processor 224 may cease the trigger
signal 244 input to the S terminal of the SR flip-flop 228, which causes
the PWM signal 268 to remain low and disconnects the power supply 246. In
some embodiments, disconnecting the power supply 246 may reduce the power
consumption of the operating coil driver circuitry 222. Similarly, the
operating driver circuitry 222 may also enable the processor 224 to
determine when the operating coil current 250 falls below the pull-in
current (e.g., duration between t4 and t5) directly from the comparator
230.

[0253] As described above, to facilitate determining when the switching
device 218 makes, the operating coil current 250 drops because the power
supply 246 is no longer sufficient to maintain the operating coil current
250 at the pull-in current due to the impedance increase in the operating
coil 220. More specifically, as the operating coil 220 draws electric
power from the DC bus 248, the voltage on the DC bus 248 (e.g., bus
voltage) may begin to droop because electric power is being drawn from
the power supply 246 faster than it is being replenished by the power
source 12. To help illustrate, FIG. 37 depicts the bus voltage 314 during
a make operation.

[0254] As described above, the operating coil current 250 begins to be
ramped up to the pull-in current at t2. As such, the electric power drawn
by the operating coil 220 increases to maintain the operating coil
current 250 at the target current (e.g., pull-in current). However, as
depicted, the bus voltage 314 begins to sag at t2. The bus voltage 314
continues to sag until some time after the switching device 218 makes at
tM. In other words, the power supply 246 may set the bus voltage 314 such
that it is sufficient to maintain the operating coil current 250 at the
pull-in current without sagging.

[0255] Based on the techniques described herein, when the switching device
218 makes may be determined based on the duration of the operating coil
current 250 drop (e.g., duration between t4 and t5). Thus, it is
important to clearly define when the PWM signal 268 is at 100% duty
cycle. However, the bus voltage 314 may affect this determination because
the bus voltage 314 affects the electric power supplied to the operating
coil 220 to make the switching device 218. Additionally, as the switching
device 218 makes, the impedance of the operating coil 220 may increase.
In other words, a higher the bus voltage 314 may enable more electric
power to be supplied, thereby decreasing the make time and increasing
rate of impedance change. On the other hand, a lower bus voltage may
enable less electric power to be supplied, thereby increasing the make
time and decreasing the rate of impedance change.

[0256] Accordingly, the bus voltage 314 may be adjusted so that sufficient
electric power may be supplied to operating coil 220 make the switching
device 218 while also causing a drop form the 100% duty cycle.
Additionally, the bus voltage 314 may be adjusted to control the duration
and/or aggressiveness of the drop in operating coil current 250. For
example, when the bus voltage 314 is higher, the drop in operating
current may be narrower shallower. On the other hand, when the bus
voltage 314 is lower, the drop in the operating current may be later,
wider, and deeper.

[0257] Thus, duration of the operating coil current drop may be adjusted
to enable the duration the PWM signal 268 is at 100% duty cycle to be
easily detected. For example, by reducing the bus voltage 314, the
duration of the current drop may be increased. Additionally, the
aggressiveness of the drop may be adjusted to ensure that the duration of
the operating coil current drop corresponds with the duration the PWM
signal 268 is at 100% duty cycle. More specifically, when the slope of
the operating coil current 250 entering or exiting the drop is less
aggressive, the possibility of the PWM signal duty cycle dropping below
100% while the operating coil current 250 is still in the drop increases.
Such stray pulses may make determining the duration of the current drop
more difficult because it is unclear at what instant the operating coil
250 enters or exits the drop. Accordingly, for example, the bus voltage
314 may be increased to increase the aggressiveness of the operating coil
current drop.

[0258] Additionally, the magnitude of the pull-in current that the
operating coil driver circuitry 222 attempts to maintain the operating
coil current 250 may also affect the drop in the operating coil current
250. More specifically, when the pull-in current is higher, the electric
power supplied is higher, thereby decreasing the make time while
increasing the power consumption of the switching device 218. In other
words, a higher pull-in current may increase rate of impedance change
and, thus, cause a more dramatic drop in the bus voltage 314. On the
other hand, when the pull-in current is lower, the electric power
supplied may be lower, thereby increasing the make time while decreasing
power consumption of the switching device 218. In other words, a lower
pull-in current may decrease rate of impedance change and, thus, cause a
less dramatic drop in the bus voltage 314.

[0259] Accordingly, an optimal balance between the bus voltage 314 and the
pull-in current may be determined to improve detection of when the
switching device 218 makes. Moreover, the optimal balance may further be
adjusted when multiple switching devices 218 make. For example, as
described above, a first switching device 218 may connect a first phase
of electric power and a second switching device 218 may connect a second
phase of electric power to an electrical motor 24 at a first time (e.g.,
based upon a predicted current zero-crossing). A third switching device
218 may then connect a third phase of electric power at to the electrical
motor 24 at a second time. To help illustrate, the first and the second
switching device 218 may close at tM and the third switching device 218
may close at tM', as depicted in FIG. 33.

[0260] As depicted, the bus voltage 314 at tM may differ from the bus
voltage at tM'. As described above, the bus voltage 314 during a make
operation may affect the operating coil current 250 drop used to detect
when the switching device 218 makes. Such effects may be compounded with
regard to the third switching device 218 because the effects of the first
and second switching device 218 are integrated through to tM'. For
example, as depicted, the electric power drawn by the first and second
switching devices 218 to make at tM sags the bus voltage 314. After tM,
the third switching device 218 continues to draw electric power and may
sag the bus voltage 314 even further. In other words, the third switching
device 218 may utilize a lower bus voltage 314 than the first and second
switching device 218.

[0261] Accordingly, in addition to adjusting the bus voltage, the pull-in
current for each switching device 218 may be individually adjusted. In
other words, an optimal balance between the bus voltage 314 and the
pull-in currents may be determined to improve detection of when each of
the switching devices 218 makes. Additionally, when switching devices 218
are closed sequentially, the timing of the make operation may be
adjusted. For example, the third switching device 218 may be closed at a
later time to enable the bus voltage 314 to recover as the power supply
246 replenishes the DC bus 248. In other words, the bus voltage 314 used
to make the third switching device 218 may be controlled by adjusting
when the third switching device 218 makes.

[0262] As described above, the temperature of the switching device 218 may
affect the make time and/or break time of the switching device 218. To
help illustrate, FIG. 38 is a plot that depicts the make time 316 versus
temperature 318. As depicted, the make time 316 of the switching device
218 increases as the temperature 318 increases. In some embodiments, the
make time may change by approximately 50 microseconds per degree Celsius.
The break time of the switching device 218 may similarly also be affected
by temperature. Accordingly, the temperature of the switching device 218
may be determined before each make operation and break operation to
facilitate determining when to apply a current profile (e.g., make
current or break current) that enables the switching device 218 to make
or break at a desired time.

[0263] Additionally, the plot depicts an impedance index 320 versus
temperature 222. More specifically, the impedance index 320 may represent
the inverse of a measured impedance of the operating coil. Since the
resistance of a conductor generally increases with temperature and the
operating coil 220 is simply a long conductive wire, the impedance of the
operating coil 220 may also increase with temperature. Accordingly, as
depicted the impedance index 320 (e.g., inverse of measured impedance)
varies inversely with temperature.

[0264] As such, the impedance of the operating coil 220 may be utilized to
determine the temperature 318 of the switching device 218. For example,
FIG. 39 depicts a process 322 for determining the temperature of the
switching device 218 during a make operation. The process 322 may be
implemented via computer-readable instructions stored in the tangible
non-transitory memory 226, 20, 46 and/or other memories and executed via
processor 224, 19, 45 and/or other control circuitry. Generally, process
322 includes applying the measurement current to the operating coil
(process block 324), determining voltage across operating coil (process
block 326), determining impedance of the operating coil (process block
328), and determining temperature of the switching device (process block
330). Process 322 may be performed before each make operation to
facilitate determining the expected make time of the switching device 218
based on temperature, as described above.

[0265] In some embodiments, the processor 224 may instruct the operating
coil driver circuitry 222 to supply the measurement current to the
operating coil 220 (process block 324). More specifically, the processor
224 may output a reference voltage (e.g., Vref) that corresponds with the
measurement current. Based at least on the comparison of the node voltage
and the reference voltage, the SR flip-flop 228 outputs a PWM signal 268
that instructs the switch 232 to supply the measurement current to the
operating coil 220 by selectively connecting and disconnecting electric
power from the DC bus 248. Accordingly, the processor 224 may determine
the operating coil voltage by multiplying the bus voltage 314 with the
duty cycle of the PWM signal 268 (process block 326).

[0266] Based on the operating coil voltage, the processor 224 may
determine the impedance of the operating coil 220 (process block 328).
More specifically, since the operating coil voltage and the operating
coil current (e.g., measurement current) are known, the processor 224 may
determine the operating coil impedance by dividing the operating coil
voltage by the measurement current and, thus, the impedance index 320.

[0267] Based on the operating coil impedance, the processor 224 may then
determine the switching device temperature 318 (process block 330). As
described above, the operating coil impedance directly relates to its
temperature 318. Accordingly, the processor 224 may determine the
temperature 318 based on that relationship. More specifically, in some
embodiments, the relationship between temperature 318 and impedance may
be defined by a manufacturer. For example, the manufacture may define a
temperature look-up-table (LUT) that takes the impedance index 320 (e.g.,
inverse of operating coil impedance) input and outputs a temperature 318.
Additionally or alternatively, in other embodiments, it may be
unnecessary to determine the exact temperature of the switching device
218. Instead, it may be sufficient to use the operating coil impedance
320 or the operating coil voltage with the operating coil current as a
proxy for temperature. In other words, the operating coil impedance 320
or the operating coil voltage with the operating coil current may be used
as inputs to the make time LUT.

[0268] Furthermore, as described above, the break operation may also be
affected by the temperature of the switching device 218. Accordingly,
FIG. 40 depicts one embodiment of a process 332 for determining the
temperature of the switching device 218 during a break operation. The
process 332 may be implemented via computer-readable instructions stored
in the tangible non-transitory memory 226, 20, 46 and/or other memories
and executed via processor 224, 19, 45 and/or other control circuitry.
Generally, the process 332 includes applying the hold-in current to the
operating coil (process block 334), determining voltage across the
operating coil (process block 336), determining impedance of the
operating coil (process block 338), and determining temperature of the
switching device (process block 340). Process 332 may be performed before
each break operation to facilitate determining the expected break time of
the switching device 218 based on temperature, as described above.

[0269] In some embodiments, the processor 224 may instruct the operating
coil driver circuitry 222 to supply the hold-in current to the operating
coil 220 (process block 334). More specifically, similar to process block
324, the processor 224 may output a reference voltage (e.g., Vref) that
corresponds with the hold-in current. Based at least on the comparison of
the node voltage and the reference voltage, the SR flip-flop 228 outputs
a PWM signal 268 that instructs the switch 232 to supply the hold-in
current to the operating coil 220 by selectively connecting and
disconnecting electric power from the DC bus 248. Accordingly, similar to
process block 326, the processor 224 may determine the operating coil
voltage by multiplying the bus voltage 314 with the duty cycle of the PWM
signal 268 (process block 336).

[0270] Similar to process block 328, the processor 224 may determine the
impedance of the operating coil 220 based on the operating coil voltage
(process block 338). More specifically, since the operating coil voltage
and the operating coil current (e.g., hold-in current) are known, the
processor 224 may determine the operating coil impedance by dividing the
operating coil voltage by the hold-in current and, thus, the impedance
index 320.

[0271] Similar to process block 330, the processor 224 may then determine
the switching device temperature 318 based on the operating coil
impedance (process block 340). As described above, the operating coil
impedance directly relates to its temperature. Accordingly, the processor
224 may determine the temperature 318 based on that relationship, which
may be defined a manufacturer. Additionally or alternatively, in some
embodiments, it may be sufficient to use the operating coil impedance or
the operating coil voltage with operating coil current as a proxy for
temperature. In other words, the impedance index 320 (e.g., inverse of
operating coil impedance) or the operating coil voltage with the
operating coil current may be used as inputs to the break time LUT.

[0272] Accordingly, based on the techniques described above, the processor
224 may use the PWM signal 268 to determine operational parameters of the
switching device 218, such as when the switching device 218 makes, when
the switching device 218 breaks, and/or the temperature of the switching
device 218. Additionally, other diagnostic information may also be
determined. For example, FIGS. 41A-C depict embodiments of determining
wellness of the switching device 218. More specifically, FIG. 41A depicts
one embodiment of a process 342 for determining wellness of the switching
device 218 with the measurement current, FIG. 41B depicts one embodiment
of a process 344 for determining wellness of the switching device 218
during a make or break operation, and FIG. 41C depicts one embodiment of
a process 346 for determining wellness of the switching device 218 with
the hold-in current. The processes 342-346 may be implemented via
computer-readable instructions stored in the tangible non-transitory
memory 226, 20, 46 and/or other memories executed via processor 224, 19,
45 and/or other control circuitry.

[0273] As shown in FIG. 41A, process 342 generally includes applying the
measurement current to the operating coil (process block 348), monitoring
the PWM signal (process block 350), and determining wellness of the
switching device (process block 352). More specifically, as described
above, the processor 224 may determine the switching device temperature
318 using the measurement current. Accordingly, the processor 224 may
detect when excessive temperatures (e.g., out of specification) are
present.

[0274] Additionally, in some embodiments, the processor 224 may detect
whether a short circuit or an open circuit condition exits in the
operating coil 220. For example, if the PWM signal duty cycle jumps to
100%, the processor 224 may determine that an open circuit condition is
present. On the other hand, if the PWM signal duty cycle is much lower
than expected, the processor 224 may determine that a short circuit
condition is present. Furthermore, the measurement current may also
monitor temperature changes in the switching device 218. For example, if
the PWM signal duty cycle begins to increase, the processor 224 may
determine that the temperature 318 is increasing. On the other hand, if
the PWM signal duty cycle begins to decrease, the processor 224 may
determine that the temperature is decreasing.

[0275] As shown in FIG. 41B, process 344 generally includes applying the
pull-in or break current to the operating coil (process block 354),
determining the make or break time of the switching device (process block
356), and determining wellness of the switching device (process block
358). More specifically, as described above, the processor 224 may
determine the expected make time and/or break time of the switching
device 218. Additionally, the processor 224 may determine the actual make
time or break time. Accordingly, the processor 224 may detect when a
faulty condition is present in the switching device 218. For example, if
the determined make time is much shorter than expected, the processor 224
may determine that the armature 118 is obstructed and not closing from a
fully open position. On the other hand, if the determined make time is
much longer than expected, the processor 224 may determine that the
armature 118 is obstructed from closing smoothly.

[0276] Additionally, the processor 224 may look at the trend of make times
or break times. More specifically, the trend may indicate the gradual
aging of the switching device 218. For example, the processor 224 may
estimate the age of the switching device (e.g., amount of life left)
based on how much the make time or break time of the switching device 218
has changed. Furthermore, as depicted in FIG. 38, the make time 316 trend
is generally linear with regard to temperature 318. Accordingly, if the
relationship begins to deviate from the expected or historical norm, the
processor 224 may determine specific changes to the switching device 218.
For example, if the make time varies unpredictably, the processor 224 may
determine that environmental conditions, such as vibrations for surround
machinery, are affecting the make times.

[0277] As shown in FIG. 41C, process 346 generally includes applying the
hold-in current to the operating coil (process block 360), monitoring the
PWM signal (process block 362), and determining wellness of the switching
device (process block 364). More specifically, as described above, the
processor 224 may determine the switching device temperature 318 using
the hold-in current. Accordingly, the processor 224 may detect when
excessive temperatures (e.g., out of specification) are present.
Additionally, since the hold-in current may be applied to the operating
coil 220 for an extended period of time, the processor 224 may also
monitor temperature changes in the switching device 218. For example, if
the PWM signal duty cycle begins to increase, the processor 224 may
determine that the temperature 318 is increasing. On the other hand, if
the PWM signal duty cycle begins to decrease, the processor 224 may
determine that the temperature is decreasing. Furthermore, in some
embodiments, if the PWM duty cycle is excessively varying, the processor
224 may determine that the armature 118 is chattering (e.g., not still).

[0278] Since the hold-in current is generally applied to the operating
coil 220 for an extended period, the hold-in current may additionally be
utilized to monitor wellness of the system 10 that includes the switching
device 218. For example, one embodiment of a process 366 for monitoring
the wellness of the system is shown in FIG. 41D. Generally, the process
366 includes applying the hold-in current to the operating coil (process
block 368), monitoring the PWM signal (process block 370), and monitoring
wellness of the system (process block 372). In other words, the processor
224 may monitor the PWM signal 268 to monitor the wellness of the system.

[0279] More specifically, electric power carried by the switching device
218 generates a magnetic field, which may act on the operating coil 220.
For example, in some embodiments, the magnetic field may induce a
positive voltage in the operating coil 220, which enables the voltage
supplied by the power source 246 to be reduced while still maintaining
the hold-in current. As such, the PWM duty cycle may decrease. On the
other hand, the magnetic field may induce a negative voltage in the
operating coil 220, which causes the power source 246 to supply larger
amount of voltage to maintain the hold-in current. As such, the PWM duty
cycle may increase.

[0280] Additionally, when the switching device 218 is closed, conducted
electric power may cause the stationary contactor assembly 124 to exert a
force on the movable contactor assembly 116. In fact, under excessive
current, the stationary contact assembly 124 may exert sufficient force
on the movable contactor assembly 116 to cause armature 118 movement. As
described above, movement may change impedance of the operating coil 220.
Accordingly, to maintain the operating coil current 250 at its target,
the duty cycle of the PWM signal may adjust to compensate for the change
in impedance. In this manner, the PWM duty cycle may facilitate detecting
excessive current conditions.

[0281] The PWM signal may also facilitate determining other
characteristics of the source electric power and/or the load. For
example, since the electric power carried may be AC, the polarity and
magnitude of the current may continuously change. As such, since the
magnitude and polarity of the induced voltage depends on the magnitude
and polarity of current being conducted, the processor 224 may determine
the phase of the current being conducted by the switching device 218
based at least in part on the changes in the PWM duty cycle. Thus, in
some embodiments, since current will be largely cyclical, the processor
224 may determine when current zero-crossings will occur.

[0282] Based on the phase of the electric power, the processor 224 may
also determine the type of load the electric power is being supplied to.
Generally, when electric power is supplied to an inductive load, the
current and the voltage will be out of phase. On the other hand, when
electric power is supplied to a resistive load, the current and voltage
will be in phase. As such, the processor 224 may determine whether the
electric power is being supplied to an inductive load or a resistive load
by comparing the phase of the current to phase of the voltage, for
example, determined using sensors 22.

Phase Sequential Switching

[0283] As described above, one or more switching devices may be used to
connect or disconnect electric power from a load 18, such as an electric
motor 24. In some embodiments, to improve control over the
connection/disconnection of electric power, the switching devices may be
single pole switching devices, such as the single pole, single current
carrying path switching devices 218. For example, three single pole
switching devices may be used in a direct on-line configuration with each
single pole switching device used to connect/disconnect one phase of
electric power. In fact, since they are single pole switching devices,
the switching devices be independently controlled, thereby enabling
various closing and/or opening sequences.

[0284] To help illustrate, a three phase direct on-line configuration is
described in 42A. As depicted, a first single pole switching device 335
may control supply of a first phase (e.g., phase A) of electric power
from the power source 12 to the load 14, a second switching device 337
may control supply of a second phase (e.g., phase B) of electric power
from the power source 12 to the load 14, and a third single pole
switching device 339 may control supply of a third phase (e.g., phase C)
of electric power from the power source 12 to the load 14. As such, the
single pole switching devices 335, 337, and 339 may be opened/closed in
various sequences.

[0285] For example, in some embodiments, the single pole switching devices
335, 337, and 339 may be controlled to sequentially open/close. One
embodiment of a process 341 for sequentially opening/closing the single
pole switching devices is described in 42B. Generally, the process 341
includes opening/closing a first switching device (process block 343),
opening/closing a second switching device (process block 345), and
opening/closing a third switching device (process block 347). In some
embodiments, process 341 may be implemented via computer-readable
instructions stored in a non-transitory article of manufacture (e.g., the
memory 226, 20, 46 and/or other memories) and executed via processor 224,
19, 45 and/or other control circuitry.

[0286] Accordingly, at a first time, control circuitry 18 may instruct the
first single pole switching device 335 to open or close (process block
343). In this manner, the first phase of electric power may be connected
or disconnected at the first time. Additionally, at a second time, the
control circuitry 18 may instruct the second single pole switching device
337 to open or close (process block 345). In this manner, the second
phase of electric power may be connect or disconnected at the second
time. Furthermore, at a third time, the control circuitry 18 may instruct
the third single pole switching device 339 to open or close (process
block 347). In this manner, the third phase of electric power may be
connected or disconnected at the third time. As such, the single pole
switching devices 335, 337, and 339 may be controlled to sequentially
connect/disconnect each phase of electric power from the power source 12
to the load 14.

[0287] In other embodiments, the single pole switching devices 335, 337,
and 339 may be controlled to open/close two and then open/close one or
open/close one and then open/close two. One embodiment of a process 349
for opening/closing two and then opening/closing one is described in 42C.
Generally, the process 349 includes opening/closing a first switching
device and a second switching device (process block 351) and
opening/closing a third switching device (process block 343). In some
embodiments, process 349 may be implemented via computer-readable
instructions stored in a non-transitory article of manufacture (e.g., the
memory 226, 20, 46 and/or other memories) and executed via processor 224,
19, 45 and/or other control circuitry.

[0288] Accordingly, at a first time, control circuitry 18 may instruct the
first single pole switching device 335 and the second single pole
switching device 337 to open or close (process block 351). In this
manner, the first phase and the second phase of electric power may be
connected or disconnected at the first time. Additionally, at a second
time, the control circuitry 18 may instruct the third single pole
switching device 339 to open or close (process block 35.). In this
manner, the third phase of electric power may be connect or disconnected
at the second time. As such, the single pole switching devices 335, 337,
and 339 may be controlled to connect/disconnect electric power from the
power source 12 to the load 14 by opening/closing two and then one.

[0289] In further embodiments, the single pole switching devices 335, 337,
and 339 may be controlled to open/close one and then open/close two. One
embodiment of a process 355 for opening/closing one and then
opening/closing two is described in 42D. Generally, the process 355
includes opening/closing a first switching device (process block 357) and
opening/closing a second switching device and a third switching device
(process block 359). In some embodiments, process 355 may be implemented
via computer-readable instructions stored in a non-transitory article of
manufacture (e.g., the memory 226, 20, 46 and/or other memories) and
executed via processor 224, 19, 45 and/or other control circuitry.

[0290] Accordingly, at a first time, control circuitry 18 may instruct the
first single pole switching device 335 to open or close (process block
357). In this manner, the first phase of electric power may be connected
or disconnected at the first time. Additionally, at a second time, the
control circuitry 18 may instruct the second single pole switching device
339 and the third single pole switching device 339 to open or close
(process block 35). In this manner, the second phase and the third phase
of electric power may be connect or disconnected at the second time. As
such, the single pole switching devices 335, 337, and 339 may be
controlled to connect/disconnect electric power from the power source 12
to the load 14 by opening/closing one and then two.

[0291] Moreover, since the single pole switching devices 335, 337, and 339
may be independently controlled, this may enable adjusting the open/close
sequence based on various desired. For example, this may be particularly
useful to implement point-on-wave (POW) techniques. More specifically,
when connecting electric power, control circuitry 18 may utilize a close
two then one sequence, thereby reducing magnitude of in-rush current
and/or current oscillations. On the other hand, when disconnecting
electric power, the control circuitry 18 may utilize an open one then two
sequence, thereby reducing likelihood and/or magnitude of arcing.

[0292] In addition to connecting/disconnecting electric power direct
on-line, the one or more switching devices (e.g., single-pole, single
current-carrying path switching devices) may be used in a wye-delta
starter, which provides electric power to the electric motor 24.
Generally, the wye-delta starter may start the electric motors 24 by
connecting the windings in a wye (e.g., star) configuration in order to
limit the amount of voltage supplied to the windings, thereby limiting in
rush current to the motor 24 and/or torque produced by the motor 24.
Subsequently, the wye-delta starter may connect the windings in the
electric motor 24 in a delta configuration after the motor 24 is started
to increase the voltage supplied to the windings, thereby increasing the
torque produced by the motor. In other words, a wye-delta starter may
ease starting of the electric motor 24 by gradually increasing supplied
electric power, thereby gradually increasing produced torque.

[0293] In some instances, opening and closing the switching devices to
transition the electric motor 24 between the various configurations may
discharge electric power (e.g., arcing), cause negative torque in the
electric motor 24, cause current spikes that could trip upstream devices,
cause current oscillations, or the like. As can be appreciated, such
events may reduce the lifespan of the switching devices, the electric
motor 24, the load, and/or other connected equipment.

[0294] As such, it would be beneficial to reduce likelihood and/or
magnitude of such events when transitioning between the various
configurations. As will be described in more detail below, one embodiment
described herein may reduce these effects by transition between the wye
configuration and the delta configuration using single-pole switching
devices, such as the single pole, single current path switching devices
218 described above. More specifically, using single-pole switching
devices may enable relatively independently controlling opening and/or
closing, for example, in a sequential manner. In other words, each of the
windings of the motor 24 may not simultaneously transition from a wye
configuration to delta configuration or vice versa.

[0295] To help illustrate, a process for sequential starting of a motor 24
using a 5-pole wye-delta starter 374 is described in reference to FIGS.
43A-H. To simplify the following discussion, the wye-delta starter 374 is
described as using five single pole switching devices, such as the
single-pole, single current-carrying path switching devices 218 described
above. However, any other suitable switching device may additionally or
alternatively be used in the techniques described herein. For example, in
some embodiments, a multi pole, multi-current carrying path switching
device (e.g., three-pole contactor) with off-set poles may be used.

[0296] It should be further noted that point-on-wave (POW) techniques may
or may not be utilized in the embodiments described below. As described
above, when POW techniques are utilized, sensors 22 may monitor (e.g.,
measure) the characteristics (e.g., voltage or current) of the electric
power supplied to the electric motor 24. The characteristics may be
communicated to the control and monitoring circuitry 18 to enable
determining the timing for making and/or breaking the switching devices
at a specific point on the electric power waveform.

[0297] More specifically, when POW techniques are utilized, a reference
point may be selected on a waveform and the timings for energizing the
coils and opening/closing switching devices may be calculated. Commands
may be sent to timers and the like based on the calculated timings. Once
the reference point is hit, the sequence may begin and the timers may
trigger the switching devices to open or close when the calculated times
are encountered (e.g., after a configurable amount of electrical degrees
and/or based a predicted current zero-crossing). In this manner, when POW
techniques are utilized, the wye-delta starter 374 may progress through
each step in a two-step start and a wye-delta phase sequential transition
based at least in part on current zero-crossings and/or predicted current
zero-crossing. On the other hand, when POW techniques are not utilized,
the wye-delta starter 374 may progress through each step in the two-step
start and the wye-delta phase sequential transition one at a time, for
example, after a brief time delay (e.g., milliseconds).

[0298] In some embodiments, continuous current flow may be provided to the
motor 24 during the transition from wye to delta (e.g., "closed
transition") by supplying current to at least one winding during the
transition. More specifically, supplying current to at least one winding
may facilitate maintaining a relationship between the rotor field and the
line electric power. In this manner, when subsequent windings are connect
to the line electric power, in rush current may be reduced, which may
obviate transition resistors.

[0299] As depicted, the 5-pole wye-delta starter 374 includes five
switching devices 376, 378, 380, 382, and 384 used to selectively connect
three motor windings 386, 388, and 390 to a three-phase power source
(e.g., mains lines 392, 394, and 396 each carrying a single phase of
power). In some embodiments, the first wye switching device 376 and the
second wye switching device 378 may have the same operational
characteristics. Additionally, the first delta switching device 380, the
second delta switching device 382, and the third delta switching device
384 may have the same operational characteristics. For example, in some
embodiments, the delta switching device 380, 382, and 384 may be
single-pole, single current carrying path switching devices 218 and the
wye switching devices 376 and 378 may be power electronic switching
devices, such as silicon-controlled rectifiers (SCRs), insulated-gate
bipolar transistors (IGBTs), or power field-effect transistors (FETs), or
other bidirectional devices.

[0300] In the depicted embodiment, dashed lines are used to indicate
non-conducting pathways and solid lines are used to indicate conducting
pathways. As such, FIG. 43A describes when each of the switching devices
376, 378, 380, 382, and 384 is open, thereby disconnecting the electric
power from the windings 386, 388, and 390. The wye-delta starter 374 may
then transition to a wye configuration using a two-step start sequence,
as described in FIGS. 43B and 43C. From the wye configuration, the
wye-delta starter 374 may then transition to a delta configuration using
phase sequential switching, as described in FIGS. 43D-H.

[0301] As described above, FIGS. 43B and 43C describe transitioning the
electric motor 24 to a wye configuration using a two-step process. More
specifically, as shown in FIG. 43B, the second wye switching device 378
may be closed to provide power to the motor windings 388 and 390. In some
embodiments, the second wye switching device 378 may be closed based at
least in part on a predicted current zero-crossing to reduce magnitude of
in rush current and current oscillations. Additionally, as shown in FIG.
43B, the first wye switching device 376 may be closed to provide
three-phase power to the motor windings 386, 388, and 390. In some
embodiments, the first wye switching device 376 may be closed after a
delay to reduce magnitude of current and/or torque oscillations, for
example, based on a predicted current zero-crossing. In this manner, the
wye-delta starter may run the electric motor 24 in the wye configuration.

[0302] After the electric motor 24 is running in the wye configuration,
current flowing through windings 386, 388, and 390 may be balanced. As
described above, the electric motor 24 may be started in the wye
configuration so that the electric motor 24 produces a reduced amount of
torque and consumes less power. In other words, as will be described in
more detail below, starting in the wye configuration enables the electric
motor 24 to be gradually started.

[0303] The wye-delta starter 374 may then transition to running the
electric motor 24 in a delta configuration to increase torque output
(e.g., ramp up the motor 24). In some embodiments, the transition to the
delta configuration may initiate after connecting in the wye
configuration, for example, to enable the electric motor 24 to reach
steady state and/or reduce magnitude of torque adjustments.

[0304] More specifically, the wye-delta starter 374 may begin transition
from the wye configuration to the delta configuration by opening the
first wye switching device 376, as shown in FIG. 43D. As a result,
electric power is only supplied to motor windings 388 and 390, which
stops the stator field. More specifically, as shown in FIG. 43E, the
first delta switching device 380 may be closed, thereby connecting first
winding 386 in the delta configuration (e.g., line 392 to line 394) while
windings 388 and 390 remain connect in the wye configuration. As a
result, the stator field may be reintroduced, thereby producing a
positive torque. In fact, in some embodiments, the closure of first delta
switching device 380 may be delayed to enable any arcing produced from
the opening first wye switching device 376 to dissipate and/or mute
adjustment between the stator field and the rotor field, for example, to
reduce magnitude of current and/or torque oscillations.

[0305] Additionally, as depicted in FIG. 43F, the second wye switching
device 378 may be opened such that only the first winding 386 continues
to receive power. In some embodiments, the opening of the second wye
switching device 378 may occur based on (e.g., at or ahead of) a current
zero-crossing in order to reduce likelihood and/or magnitude of arcing.

[0306] Furthermore, the second delta switching device 382 may be closed
after the opening of the second wye switching device 378, thereby
providing power to second winding 388 as depicted in FIG. 43G. More
specifically, when the second wye switching device 378 is open, the
stator field stops rotating and while the speed strength of the rotor
field gradually diminishes. Thus, waiting too long to close second delta
switching device 382 may increase inrush current and/or cause the rotor
field to pass the stator field, thereby producing a whipsaw effect of
braking torque as the stator and rotor fields try to sync.

[0307] Accordingly, in some embodiments, the closure timing of second
delta switching device 382 may be a short delay (e.g., a few milliseconds
or a configurable number of electrical degrees) after second wye
switching device 378 opens to reduce the likelihood of the rotor field
passing the stator field. For example, the second delta switching device
382 may close based upon where a predicted current zero-crossing.
Additionally, the closure timing of second delta switching device 382 may
enable any arcing resulting from the opening of second wye switching
device 378 to be extinguished before closing. For example, in some
embodiments, second delta switching device 382 may be closed two hundred
forty electrical degrees after the first delta switching device 380
closure.

[0308] As depicted in FIG. 43H, the third delta switching device 384 may
be closed. In some embodiments, the third delta switching device 384 may
close based upon a predicted current-zero crossing. Once the third delta
switching device 384 is closed, three-phase power is supplied to the
three motor windings 386, 388, and 390 via the closed switching devices
380, 382, and 384 in the delta configuration. As such, the motor 24 may
accelerate to full torque capabilities in the delta configuration.

[0309] Although each switching device 376, 378, 380, 382, and 384 is
described as sequentially opening or closing, in other embodiments one or
more of the switching devices may open or close substantially
simultaneous. For example, in some embodiments, switching devices 382 and
384 may be closed substantially simultaneously. In this manner, an
interim torque levels may be removed and the motor may accelerate to full
load faster.

[0310] One embodiment of a process 398 for controlling the wye-delta
starter 374 to transition an electric motor 24 from an open configuration
to a wye configuration and to a delta configuration is described in FIG.
44A. Generally, the process 398 includes closing a second wye switching
device 378 (process block 399) and closing a first wye switching device
376 after closing first wye switching device 376 (process block 400) to
run the electric motor 24 in the wye configuration. Additionally, the
process 398 includes opening the first wye switching device 376 (process
block 401), closing a first delta switching device 380 after the first
wye switching device 376 opens (process block 402), opening the second
wye switching device 378 (process block 404), closing a second delta
switching device 382 after the first delta switching device 380 closes
(process block 406), and closing a third delta switching device 384 after
the first delta switching device 380 closes (process block 408) to run
the electric motor 24 in the delta configuration. In some embodiments,
process 398 may be implemented via computer-readable instructions stored
in a non-transitory article of manufacture (e.g., the memory 226, 20, 46
and/or other memories) and executed via processor 224, 19, 45 and/or
other control circuitry.

[0311] In some embodiments, process 398 may begin when the wye-delta
starter 374 is in the open configuration, thereby disconnecting
electrical power from the electric motor 24 (e.g., FIG. 43A). To connect
the electric motor 24 in the wye-configuration, control circuitry 18 may
instruct the second wye switching device 378 to close (process block 399)
and the first wye switching device 376 to close after closure of the
second wye switching device 378 (process block 400). In some embodiments,
the control circuitry 18 may instruct the wye switching devices 376 and
378 to close based at least in part on a predicted current zero-crossing
and/or at a configurable number of electrical degrees apart from each
other. For example, the control circuitry 18 may instruct second wye
switching device 378 to close at a line-to-line voltage maximum (e.g., a
predicted current zero-crossing) and the first wye switching device 376
to close sixty electrical degrees later (e.g., a predicted current
zero-crossing), thereby reducing magnitude of in-rush current and/or
current oscillations.

[0312] From the wye configuration, control circuitry 18 may instruct the
first wye switching device 376 to open (process block 401). In some
embodiments, the control circuitry 18 may instruct the first wye
switching device 376 to open based at least in part on a current
zero-crossing (e.g. at or before a current zero-crossing), which may
reduce arcing and extend the life of the first wye switching device 376,
the electric motor 24, the load, and/or other connected electrical
components.

[0313] After first wye switching device 376 is opened, control circuitry
18 may instruct the first delta switching device 380 to close (process
block 402). In some embodiments, the control circuitry 18 may instruct
the first delta switching device 380 to close based at least in part on a
predicted current zero-crossing and/or at a configurable number of
electrical degrees after the first switching device 376 opens. For
example, in some embodiments, the control circuitry 18 may instruct first
delta switching device 380 to close thirty electrical degrees (e.g., a
predicted current zero-crossing) after first wye switching device 376 is
opened.

[0314] Control circuitry 18 may then instruct second wye switching device
378 to open (process block 404). In some embodiments, the control
circuitry 18 may instruct second wye switching device 378 to open based
at least in part on a next subsequent current zero-crossing, thereby
reducing likelihood and/or magnitude of arcing and current spikes.

[0315] Additionally, after first delta switching device 380 is closed, the
control circuitry 18 may instruct second delta switching device 382 to
close (process block 406) and third delta switching device 384 to close
(process block 408). In some embodiments, the control circuitry 18 may
instruct second delta switching device 382 and third delta switching
device 384 to close based at least in part on a predicted current
zero-crossing and/or at a configurable number of electrical degrees after
the first wye switching device 376 opened. For example, the control
circuitry 18 may instruct second delta switching device 382 to close a
two hundred forty electrical degrees (e.g., a predicted current
zero-crossing) after the first delta switching device 380 closure and
instruct third delta switching device 384 to close four hundred twenty
electrical degrees (e.g., a predicted current zero-crossing) after the
first delta switching device 380 closure.

[0316] In some embodiments, it may be desirable to close the second delta
switching device 382 quickly because the stator field may stall after the
second wye switching device 378 opens. As such, waiting an extended
period before closing second delta switching device 382 may result in the
rotor field to passing the stator field, which may lead to torque
oscillations (e.g., a whipsaw effect) as the fields try to sync and/or
current spikes in the motor 24.

[0317] In this manner, the control circuitry 18 may instruct the wye-delta
starter 374 to gradually transition an electric motor 24 from the open
configuration to the wye-configuration and to the delta-configuration. In
other words, the wye-delta starter 374 may be controlled to gradually
adjust speed and/or or torque of the motor 24 by sequentially
opening/closing the switching devices 376-384.

[0318] Additionally, it should be noted that the described electrical
degrees are merely intended to be illustrative. In fact, in some
embodiments, the number of electrical degrees may be dynamically adjusted
by the control circuitry 18 and/or firmware of the switching devices
based at least in part on supplied electrical power, application (e.g.,
load), environmental factors (e.g., dust, condition of switching devices
and/or load, etc.), and so forth. For example, as described above, the
timing of opening/closing a switching device may be adjusted to reduce
likelihood of arcing, magnitude of arcing, magnitude of current
oscillations, magnitude of torque oscillations, magnitude of in-rush
current, likelihood of current spikes, magnitude of current spikes, or
any combination thereof. Additionally, in some embodiments, the timings
may be adjusted based at least in part on the type of application the
electric motor 24 is used in. For example, when driving a chiller, long
delays may not be acceptable because and, thus, the adjusted to be
shorter. Further, the timings may be adjusted based at least in part on
the power factor of the AC electric power system.

[0319] To facilitate, the timings may be adjusted by multiples of thirty
electrical degrees (e.g., thirty, sixty, ninety, etc.), multiples of one
hundred eighty electrical degrees (e.g., one hundred eighty, three
hundred sixty), multiples of three hundred sixty degrees, multiples of
seven hundred twenty degrees, or so forth. In fact, delaying the timings
may enable electric power to stabilize, thereby reducing magnitude of
current oscillations and/or current spikes. More specifically, a lower
magnitude of current oscillation and/or current spikes may improve
adjustments between the stator field and the rotor field. As such, in
some embodiments, the timing of each subsequent opening/closing may be
based at least in part on when electric power supplied to the windings
386, 388, and 390 stabilize.

[0320] To help illustrate, a plot 409 of magnitude of current supplied to
the electric motor 24 is described in FIG. 44B. More specifically, the
plot 409 includes a current curve 411 that describes magnitude of current
supplied to windings 386, 388, and 390 in the electric motor between t0
when motor 24 is connect in an open configuration (e.g., FIG. 43A) to t7
when the motor 24 is connected in a delta configuration (e.g., FIG. 43H).

[0321] As described by the current curve 411, the magnitude of current
supplied to the electric motor 24 is zero between t0 and t1. Thus,
between t0 and t1, the wye-delta starter 374 may be in the configuration
described in FIG. 43A, thereby disconnecting electric power from the
windings 386, 388, and 390. Additionally, the magnitude of current
supplied to the electric motor 24 increases at t1 and reaches a steady
state before t2. Thus, between t1 and t2, the wye-delta starter 374 may
be in the configuration described in FIG. 43B, thereby connecting
electric power to windings 388 and 390 in the wye configuration.
Furthermore, the magnitude of current supplied to the electric motor 24
again increases at t2 and reach a steady state before t3. Thus, between
t2 and t3, the wye-delta starter 374 may be in the configuration
described in FIG. 43C, thereby connecting electric power to each of the
windings 386, 388, and 390 in the wye configuration.

[0322] As described by the current curve 411, the magnitude of the current
supplied to the electric motor 24 may decrease at t3 and reach a steady
state before t4. Thus, between t3 and t4, the wye-delta starter 374 may
be in the configuration described in FIG. 43D, thereby connecting
electric power to windings 388 and 390 in the wye configuration.
Additionally, the magnitude of the current supplied to the electric motor
24 may increase at t4 and reach a steady state before t5. Thus, between
t4 and t5, the wye-delta starter 374 may be in the configuration
described in FIG. 43E, thereby connecting electric power to windings 388
and 390 in the wye configuration and first winding 386 in the delta
configuration.

[0323] Furthermore, the magnitude of current supplied to the electric
motor 24 may be again increased at t5 and reach a steady state before t6.
In some embodiments, between t5 and t6, the wye-delta starter 374 may
operate such that, at a first time, the second winding 388 is connected
in the wye configuration, first winding 386 is connected in a delta
configuration, and third winding 390 is connected in both the wye and the
delta configuration and, at a second time, the second winding 388 remains
connected in the wye configuration and windings 386 and 388 are connected
in the delta configuration. In other embodiments, between t5 and t6, the
wye delta starter 384 may operate such that, at a first time, the first
winding 386 is connected in the delta configuration (e.g., FIG. 43F) and,
at a second time, windings 386 and 388 are connected in the delta
configuration (e.g., FIG. 43G).

[0324] As described by the current curve 411, the magnitude of the current
supplied to the electric motor 24 may increase at t6 and reach a steady
state before t7. Thus, between t6 and t7, the wye-delta starter 374 may
be in the configuration described in FIG. 43H, thereby connecting
electric power to windings 386, 388 and 390 in the delta configuration.
Thus, in the described embodiment, the timing of opening/closing of the
switching devices 376-384 may be determined such that subsequent
opening/closing is performed after the electric motor 24 stabilizes
(e.g., magnitude of current reaches a steady state), thereby reducing
magnitude of current spikes, current oscillations, and/or torque
oscillations produced by sequential switching.

[0325] Moreover, in some embodiments, POW techniques may also be utilized
to improve sequential switching of the wye-delta starter 374. As
described above, when POW techniques are utilized, the wye-delta starter
374 may progress through each step in the sequential switching based at
least in pat on current zero-crossings and/or predicted current
zero-crossings. To help illustrate, current and voltage waveforms of the
power source 12 and the windings 386, 388, and 390 are described.

[0326] Since connecting the windings 386, 388, and 390 in a wye
configuration is essentially connecting three phase electric power, the
current and voltage waveforms describing transitioning from disconnected
to the wye configuration are described in relation to FIGS. 5A-5C between
t0 and t2. In this context, FIG. 5A illustrates the voltage of
three-phase electric power (e.g., a first phase voltage curve 66, a
second phase voltage curve 68, and a third phase voltage curve 70)
provided by a power source 12. FIG. 5B illustrates the line to neutral
voltage supplied to each terminal (e.g., first terminal voltage curve 72,
second terminal voltage curve 74, and third terminal voltage curve 76) of
the electric motor 24. FIG. 5C illustrates line current supplied to each
winding (e.g., first winding current curve 77, second winding current
curve 78, and third winding current curve 80) of the electric motor 24.

[0327] As described above, between t0 and t1, the switching devices
376-384 are open and electric power is not connected to the electric
motor 24. At t1, the second wye switching device 378 is closed to connect
a first phase (e.g., phase A) and a second phase (e.g., phase B) of the
electric power to the second winding 388 and the third winding 390 in the
wye configuration. To reduce magnitude of in-rush current and/or current
oscillations, the wye-delta starter 374 may close the second wye
switching device 278 based at least in part on a predicted current
zero-crossing (e.g., within a range from slightly before to slightly
after the predicted current zero-crossing).

[0328] As described above, a predicted current zero-crossing may
correspond with a line-to-line voltage maximum (e.g., 90.degree. after a
voltage zero-crossing). With regard to FIG. 5A, the predicted current
zero-crossing occurs approximately when the line-to-line voltage between
the second phase (e.g., second phase voltage curve 68) and the third
phase (e.g., third phase voltage curve 70) is at a maximum. Accordingly,
by closing the second wye switching device 278 at t1, electric power is
connected to the second winding 388 and the third winding 390 at
approximately the predicted current zero-crossing. In fact, as depicted
in FIG. 5C, since electric power is connected based at least in part on a
predicted current zero-crossing, the current supplied to the second
winding 388 (e.g., second winding current curve 79) and the third winding
390 (e.g., second winding current curve 80) start at zero and gradually
change, thereby reducing magnitude of in-rush current and/or current
oscillation.

[0329] After second wye switching device 378 is closed, first wye
switching device 376 is closed at t2 to supply the third phase (e.g.,
phase C) of the electric power to the first winding 386 in the wye
configuration. To reduce magnitude of in-rush current and/or current
oscillations, the wye-delta starter 374 may connect electric power to the
first winding 386 based at least in part on a predicted current
zero-crossing. With regard to FIG. 5A, the predicted current
zero-crossing occurs when the sum of line-to-line voltage between the
first phase (e.g., first phase voltage curve 66) and the third phase
(e.g., third phase voltage curve 70) and the line-to-line voltage between
the first phase (e.g., second phase voltage curve 66) and the second
phase (e.g., third phase voltage curve 68) is at a maximum. Accordingly,
by closing the first wye switching device 376 at t2, electric power is
connected to the first winding 386 at approximately the predicted current
zero-crossing. In fact, as depicted in FIG. 5C, since the electric power
connected based at least in part on a predicted current zero-crossing,
the current supplied to the first winding 386 (e.g., first winding
current curve 78) starts at zero and gradually change, thereby rotating
the electric motor 24 and reducing magnitude of in-rush current and/or
current oscillation.

[0330] To further illustrate, FIGS. 45A-C depicts current and voltage
waveforms for transitioning from the wye configuration to the delta
configuration. Specifically, FIG. 45A illustrates the line to neutral
voltage supplied to each terminal (first terminal voltage curve 414,
second terminal voltage curve 412, and third terminal voltage curve 416)
of the electric motor 24. Additionally, 45B illustrates the voltage of
three-phase electric power (e.g., a first phase voltage curve 420, a
second phase voltage curve 418, and a third phase voltage curve 422)
provided by a power source 12. FIG. 45C illustrates line current supplied
to each winding (e.g., first winding current curve 422, second winding
current curve 424, and third winding current curve 426) of the electric
motor 24.

[0331] As described above, the first wye switching device 376 is opened at
t3 to disconnect electric power from the first winding 386. To reduce the
likelihood and/or magnitude of arcing, the wye-delta starter 374 may open
the first wye switching device 376 based at least in part of a current
zero-crossing (e.g., at or slightly before the current zero-crossing).
With regard to FIG. 45C, the current zero-crossing occurs when current
supplied to the first winding 386 (e.g., first winding current curve 422)
is zero. Accordingly, by opening the first wye switching device 376 at
t3, electric power is disconnected from the first winding 386 at
approximately the current zero-crossing.

[0332] After the first wye switching device 376 is opened, first delta
switching device 380 may be closed at t4 to connect electric power to the
first winding 386 in the delta configuration. To reduce magnitude of
in-rush current and/or current oscillations, the wye-delta starter 374
may close the first delta switching device 380 based at least in part on
a predicted current zero-crossing (e.g., within a range from slightly
before to slightly after the predicted current zero-crossing). With
regard to FIG. 45B, the predicted current zero-crossing occurs halfway
between t3 and t4 when the sum of line-to-line voltage between the first
phase (e.g., first phase voltage curve 420) and the third phase (e.g.,
third phase voltage curve 416) and the line-to-line voltage between the
first phase (e.g., second phase voltage curve 420) and the second phase
(e.g., second phase voltage curve 418) is at a maximum. Accordingly, by
closing the first wye switching device 376 at t4, the first wye switching
device 376 is closed slightly after the predicted current zero-crossing.
Nevertheless, as depicted in FIG. 45C, since electric power is connected
based at least in part on the predicted current zero-crossing, the
current supplied to the first winding 386 (e.g., first winding current
422) starts at zero and gradually changes, thereby reducing magnitude of
in-rush current and/or current oscillation.

[0333] Furthermore, at t4, the electric motor windings 386-390 are
connected in a mixed wye-delta configuration. Accordingly, as depicted in
FIG. 45C, the current supplied to the windings (e.g., first winding
current curve 422, second winding current curve 424, and third winding
current curve 426) is unbalanced, which may cause the winding (e.g., 388
and 390) connected in wye and the winding (e.g., 386) connected in delta
to produce varying magnetic fields. In other words, the electric motor 24
may be unbalanced while still producing a positive torque.

[0334] After first delta switching device 380 is closed, second wye
switching device 378 may be opened and second delta switching device 382
may be closed at t5 to connect the second winding 388 in the delta
configuration. To reduce the likelihood and/or magnitude of arcing, the
wye-delta starter 374 may open the second wye switching device 378 based
at least in part of a current zero-crossing. With regard to FIG. 45C, the
current zero crossing occurs when current supplied to the second winding
388 (e.g., second winding current curve 424) and the third winding 390
(e.g., third winding current curve 426) are zero. Accordingly, by opening
the second wye switching device 378 at t5, the second and third windings
388 and 390 are disconnected approximately at the current zero-crossing.

[0335] Additionally, to reduce magnitude of in-rush current and/or current
oscillations, the wye-delta starter 374 may close the second delta
switching device 382 based at least in part on a predicted current
zero-crossing. With regard to FIG. 45B, the predicted current
zero-crossing occurs at a line-to-line voltage maximum between the first
phase (e.g., first phase voltage curve 420) and the second phase (e.g.,
second phase voltage curve 418). Accordingly, by closing the second delta
switching device 382 at approximately t5, electric power is connect to
the second winding 388 at approximately the predicted current
zero-crossing. In fact, as depicted in FIG. 45C, since electric power is
connected based at least in part on the predicted current zero-crossing,
the current supplied to the second winding 388 (e.g., second winding
current 424) starts at zero and gradually changes, thereby reducing
magnitude of in-rush current and/or current oscillation.

[0336] After first delta switching device 380 is closed, the third delta
switching device 384 is may be close at t6. To reduce magnitude of
in-rush current and/or current oscillations, the wye-delta starter 374
may close the third delta switching device 384 based at least in part on
a predicted current zero-crossing. With regard to FIG. 45B, the predicted
current zero-crossing occurs when the sum of line-to-line voltage between
the first phase (e.g., first phase voltage curve 420) and the third phase
(e.g., third phase voltage curve 416) and the line-to-line voltage
between the third phase (e.g., third phase voltage curve 416) and the
second phase (e.g., second phase voltage curve 418) is at a maximum.
Accordingly, by closing the third delta switching device 384 at t6,
electric power is connect to the third winding 390 at approximately the
predicted current zero-crossing. In fact, as depicted in FIG. 45C, since
electric power is connected based at least in part on the predicted
current zero-crossing, the current supplied to the third winding 390
(e.g., third winding current 426) starts at zero and gradually changes,
thereby reducing magnitude of in-rush current and/or current oscillation.

[0337] Thus, in the described embodiment, the timing of opening/closing of
the switching devices 376-384 may be determined such based at least in
part on current zero-crossings and/or predicted current zero-crossings.
As discussed above, this may facilitate reducing in-rush current and/or
current oscillations when a switching device is closed and reduce
likelihood and/or magnitude of arcing when a switching device is open. In
this manner, the wye-delta starter 374 may utilize sequential switching
to gradually adjust speed and/or torque of the electric motor 24,
particularly during startup.

[0338] In fact, the timing of the sequential switching may also be
determined based on a balance between desired ramp up duration, strain on
the motor 24, and/or strain on the load 14. For example, in some
embodiments, to reduce ramp up duration, the wye-delta starter 374 may
adjust configuration of the first wye switching device 376-382 as soon as
magnitude of the supplied current stabilizes. Additionally, to reduce
strain on the motor 24, the wye-delta starter 374 may remain at each
configuration a differing duration. For example, duration that the
electric motor 24 is run a wye configuration (e.g., between t2 and t3)
may be longer than duration that the electric motor 24 is run in a mixed
wye-delta configuration (e.g., between t3 and t4). In some embodiments,
duration that the electric motor 24 is run in a first mixed wye-delta
configuration (e.g., between t4 and t5) may be longer than duration that
the electric motor 24 is run in a second mixed wye-delta configuration
(e.g., between t3 and t4).

[0339] Once in the delta configuration, the wye-delta starter 374 may
enable the electric motor 24 to utilize maximum (e.g., 100%) torque
and/or maximum (e.g., 100%) speed capabilities. In other words, the
torque and/or speed capabilities of the electric motor 24 may be
increased when running in the delta configuration as compared to running
in the wye configuration. However, power consumption by the electric
motor 24 may also be increased. As such, in certain scenarios, it may be
beneficial for the wye-delta starter 374 to transition the motor 24 from
the delta configuration back to the wye configuration, thereby reducing
power consumption.

[0340] One embodiment of a process 428 that describes the transition
between wye to delta and vice versa is shown in FIG. 46. Generally, the
process 428 includes the same steps 401-408 shown in FIG. 44A to phase
sequentially switch from wye to delta. To transition from delta to wye,
the process 428 includes opening the third delta switching device 384
(process block 430), opening the second delta switching device 382
(process block 432), closing the second wye switching device 378 after
the second delta switching device 382 opens (process block 434), opening
the first delta switching device 380 (process block 436), and closing the
first wye switching device 376 after the second wye switching device 378
closes (process block 438). In some embodiments, the process 428 may be
implemented via computer-readable instructions stored in a tangible
non-transitory article of manufacture (e.g., the memory 226, 20, 46
and/or other memories) and executed via processor 224, 19, 45 and/or
other control circuitry.

[0341] As previously noted, when POW techniques are not utilized the
wye-delta starter may progress through each step in the sequential
switching after a brief time delay (e.g., milliseconds) or substantially
simultaneously. On the other hand, when POW techniques are utilized the
wye-delta starter may progress through each step in the wye two-step
start and phase sequential wye-delta switching after a configurable
number of electrical degrees and/or based at least in part on current
zero-crossings.

[0342] Turning now to the process 428, the phase sequential wye-delta
switching process blocks (process blocks 401, 402, 404, 406, and 408)
described above with reference to FIG. 44A are reproduced in order to aid
in understanding how the techniques enable sequentially switching back
and forth between wye and delta as desired. As such, the detailed
description of each process block in the phase sequential wye-delta
switching in FIG. 44A is incorporated here by reference.

[0343] Thus, at process block 408, the electric motor 24 is running in a
delta configuration. From the delta configuration, control circuitry 18
may instruct third delta switching device 384 to open (process block 430)
and instruct second delta switching device 382 to open (process block
432). In some embodiments, the control circuitry 18 may instruct third
delta switching device 384 and second delta switching device 382 to open
based at least in part on current zero-crossings (e.g., slightly before
or at the current zero-crossings) to reduce likelihood and/or magnitude
of arcing. Additionally or alternatively, the control circuitry 18 may
instruct the third delta switching device 384 to open at any time while
the electric motor 24 is running in the delta configuration. For example,
in some embodiments, third delta switching device 384 may be opened first
and second delta switching device 382 opened subsequently. In other
embodiments, both of the switching devices 382 and 384 may be opened
simultaneously. After both the switching devices 382 and 384 are opened,
the electric power is only connect to the first winding 386 connected in
the delta configuration.

[0344] After switching devices 382 and 384 are opened, the control
circuitry 18 may instruct the second wye switching device 378 to close
(process block 434). In some embodiments, the control circuitry 18 may
instruct second wye switching device 378 to based at least in part on a
predicted current zero-crossing after the wye switching devices are
opened. Once second wye switching device 378 is closed, the motor may be
running in a mixed wye-delta configuration with first winding 386 in
connected in the delta configuration and windings 388 and 390 connected
in the wye configuration. As a result, as discussed above, the winding
currents may be unbalanced.

[0345] Then, control circuitry 18 may instruct the first delta switching
device 380 to open (process block 436). In some embodiments, the control
circuitry 18 may instruct first delta switching device 380 to open based
at least in part on a current zero-crossing (e.g., slightly before or at
the current zero-crossing) to reduce magnitude and/or likelihood of
arcing. Opening the first delta switching device 380 may remove power
from the first winding 386. As such, at this point, windings 388 and 390
may be supplied power in the wye configuration.

[0346] Additionally, after first delta switching device 378 is opened,
control circuitry 18 may instruct first wye switching device 376 to close
(process block 438). In some embodiments, the control circuitry 18 may
instruct first wye switching device 376 to close based at least in part
on a predicted current zero-crossing. Once the first wye switching device
376 closes, the electric motor 24 may be running in the wye
configuration. As a result, the current in windings 386, 388, and 390 may
be balanced and the amount of power consumed and torque produced may be
reduced.

[0347] It should be noted that once the electric motor 24 is running in
the wye configuration, the process 428 enables phase sequentially
switching back to delta configuration by returning to process block 401.
In this manner, the wye-delta starter 374 may transition running the
electric motor 24 in either configuration (e.g., wye or delta) as desired
(represented by arrows 440).

[0348] In the above described embodiments, the five switching device are
utilized in the wye-delta starter 374. As such, the above wye-delta
starter 374 may be referred to herein as a 5-pole wye-delta starter.
However, in other embodiments, it may be possible to increase amount of
control over electric power supplied to the electric motor 24 by
increasing number of switching devices utilized in the wye-delta starter.
For example, in some embodiments, six switching devices may be utilized.
Thus, such a wye-delta starter may be referred to herein as a 6-pole
wye-delta starter. As will be described in more detail below, a 6-pole
wye-delta starter may further extend the life span of the switching
devices by enabling the switching devices to take turns when switching.

[0349] To help illustrate, a 6-pole wye-delta starter 442 is described in
FIGS. 47A-G. To simplify the following discussion, the wye-delta starter
442 is described as using single pole switching devices, such as the
single-pole, single current-carrying path switching devices 218 described
above. However, any other suitable switching device may additionally or
alternatively be used in the techniques described herein. For example, in
some embodiments, a multi-pole, multi-current carrying path switching
device (e.g., three-pole contactor) with off-set poles may be used.

[0350] As with the 5-pole wye-delta starter 374, is defined by the circuit
diagrams 442 FIGS. 47A-G. It should be further noted that point-on-wave
(POW) techniques may or may not be utilized in the embodiments described
below. As described above, when POW techniques are utilized, sensors 22
may monitor (e.g., measure) the characteristics (e.g., voltage or
current) of the electric power supplied to the electric motor 24. The
characteristics may be communicated to the control and monitoring
circuitry 18 to enable determining the timing for making and/or breaking
the switching devices at a specific point on the electric power waveform.

[0351] As depicted, the 6-pole wye-delta starter 442 includes six
switching devices 444, 446, 448, 450, 452, and 454 used to selectively
connect three motor windings 456, 458, and 460 to a three-phase power
source (e.g., mains lines 462, 464, and 466 each carrying a single phase
of power). In some embodiments, the first wye switching device 444, the
second wye switching device 446, and the third wye switching device 448
may have the same operational characteristics. Additionally, the first
delta switching device 450, the second delta switching device 452, and
the third delta switching device 454 may have the same operational
characteristics. For example, in some embodiments, the first delta
switching device 450, 452, and 454 may be single-pole, single current
carrying path switching devices 218 and the wye switching devices 444,
446, and 448 may be power electronic switching devices, such as
silicon-controlled rectifiers (SCRs), insulated-gate bipolar transistors
(IGBTs), power field-effect transistors (FETs), and/or other
bidirectional devices.

[0352] In the depicted embodiment, dashed lines are used to indicate
non-conducting pathways and solid lines are used to indicate conducting
pathways. As such, FIG. 47A describes when each of the switching devices
444, 446, 448, 450, 452, and 454 is open, thereby disconnecting the
electric power from the windings 456, 458, and 460. The wye-delta starter
442 may then transition to a wye configuration using a two-step start
sequence, as described in FIGS. 47B and 47C. From the wye configuration,
the wye-delta starter 442 may then transition to a delta configuration
using phase sequential switching, as described in FIGS. 47D-H.

[0353] The steps in the phase sequential wye-delta transition using 6-pole
wye-delta starter 442 is essentially the same as the 5-pole wye-delta
starter 374, which is shown in FIGS. 43A-G. However, the 6-pole wye-delta
starter utilizes three wye switching devices (444, 446, and 448), as
opposed to two. As such, the order in which the wye switching devices are
closed in the wye two-step start and the order in which the wye switching
devices are opened in the phase sequential wye-delta switching may
change. In particular, regarding the wye two-step start, in order to
provide current to the windings using three wye switching devices, one of
the steps may close two wye switching devices simultaneously, and the
other step may close the third switching device. For example, as depicted
in FIG. 47B, the switching devices 446 and 448 may close simultaneously
to connect windings 458 and 460 from line 464 to line 466. Subsequently,
as depicted in FIG. 47C, the first wye switching device 444 may close,
thereby connecting the windings 454, 456, and 458 in the wye
configuration.

[0354] Once the electric motor 24 is running in wye configuration, the
phase sequential switching to delta may initiate. As with the 5-pole
wye-delta starter 374, one of the wye switching devices 444 may be opened
as shown in FIG. 47D. Next, as shown in FIG. 47E, the first delta
switching device 450 may be closed to connect the first winding 456 in
the delta configuration. After switching device 450 closes, the motor 24
may be running in a mixed wye-delta configuration with first winding 456
connected in delta and windings 458 and 460 connected in wye. Then, as
shown in FIG. 47F, the remaining two closed wye switching devices 446 and
448 may be opened, for example, sequentially or simultaneously.
Subsequently, switching devices 452 and 454 may be closed either one
after the other, as shown in FIGS. 47F and 47G, or simultaneously.

[0355] It should be noted that utilizing three wye switching devices (444,
446, and 448) may enable wear balancing by keeping track of which
switching device(s) opened first. In some embodiments, the first
switching device that opens may experience a larger amount of wear
compared to the subsequently opened switching devices. As such, the
switching device that opens first may be rotated during subsequent
sequential wye-delta transitions to even out the wear on the switching
devices and lengthen the lifespan of the switching devices. In other
embodiments, the order that the wye switching devices opens may be
determined by statistically by randomizing the order, which may obviate
persistent memory.

[0356] For example, in the depicted embodiment shown in FIGS. 47D-F, the
first wye switching device 444 may be opened first to disconnect electric
power from the first winding 456. In certain embodiments, control and
monitoring circuitry 18 connected to the wye-delta starter may record
that the first wye switching device 444 opened first. Then, the next time
phase sequential wye-delta switching is initiated, the control and
monitoring circuitry 18 may determine that the first wye switching device
444 opened first previously and, thus, instruct the second wye switching
device 446 or the third wye switching device 448 to open first. For
example, since switching device 444 opened first previously, the control
and monitoring system 18 may instruct the second wye switching to open
first in a subsequent wye to delta transition.

[0357] Similar wear balancing may be performed when phase sequentially
switching from the delta configuration back to the wye configuration. For
example, in some embodiments, the first delta switching device 450 may be
opened first to disconnect electric power from the first winding 456. In
certain embodiments, control and monitoring circuitry 18 connected to the
wye-delta starter may record that the first delta switching device 450
opened first. Then, the next time phase sequential wye-delta switching is
initiated, the control and monitoring circuitry 18 may determine that the
first delta switching device 450 opened first previously and, thus,
instruct the second delta switching device 452 or the third delta
switching device 454 to open first. For example, since switching device
450 opened first previously, the control and monitoring system 18 may
instruct the second delta switching device 452 to open first in a
subsequent delta to wye transition.

[0358] With the foregoing in mind, FIG. 48 depicts an embodiment of a
process 468 for wye-delta motor starting over a series of starts.
Generally, the process 468 includes receiving a signal to start the motor
(process block 470), selecting the switching device to close and/or open
first (process block 472), executing phase sequential wye-delta switching
and close and/or open the selected switching device (process block 474),
and recording which switching device was selected and opened and/or
closed first (process block 476). In some embodiments, process 468 may be
implemented via computer-readable instructions stored in the tangible,
non-transitory memory 226, 20, 46 and/or other memories and executed via
processor 224, 19, 45 and/or other control circuitry.

[0359] The process 468 may enable wear balancing for various configuration
of switching devices performing various switching operations. However, to
help illustrate, the process 468 is described in relation to transition
from the wye configuration to the delta configuration using the 6-pole
wye-delta starter 442. For example, the control and monitoring circuitry
18 may receive a signal to transition from the wye configuration to the
delta configuration (process block 470). As described above, the wye
delta starter 442 may transition from the wye configuration to the delta
configuration by first opening a wye switching device 444, 446, or 448.

[0360] Accordingly, the control and monitoring circuitry 18 may select one
of the wye switching devices 444, 446, and 448 to open first (process
block 472). As described above, the control and monitoring circuitry 18
may select which wye switching device to open first based at least in
part on previous open operations. For example, when the first wye
switching device 444 was opened first in a previous operating, the
control and monitoring system 18 may select the second wye switching
device 446 or the third wye switching device 448 to open first.
Additionally, if this is the first time switching operating, the control
and monitoring circuitry 18 may select one of the wye switching devices
444, 446, or 448 as a default.

[0361] The control and monitoring circuitry 18 may instruct the selected
wye switching device to open (process block 474). Additionally, the
control and monitoring circuitry 18 may instruct the remaining switching
devices to open or close to perform the transition from the wye
configuration to the delta configuration.

[0362] Furthermore, the control and monitoring circuitry 18 may keep a
record of the selected wye switching device to facilitate determining
which switching device to select in subsequent switching operations
(process block 476). In some embodiments, the switching device that
opened first may be stored in memory 226, 20, or 46. In this manner, when
another signal to transition from the wye configuration to the delta
configuration is received, the control and monitoring circuitry 18 may
retrieve the switching order used in the previous operation (arrow 478).

[0363] Based at least in part on the previous switching order, the control
and monitoring circuitry 18 may select a different wye switching device
444, 446, or 448 to open first (process block 472). Subsequently, the
control and monitoring circuitry 18 may instruct the selected wye
switching device to open (process block 472) and the remaining switching
devices to open or close to perform the transition from the wye
configuration to the delta configuration.

[0364] Moreover, the techniques described herein may be extended to other
wye-delta configurations. For example, FIGS. 49A and 49B depict circuit
diagrams for 8 and 9 pole wye-delta switching arrangements, respectively.
In particular, the circuit diagram 480a depicted in FIG. 49A includes two
wye switching devices 482 and 484 and three delta switching devices 486,
488, and 490, and three mains switching devices 492a, 494a, and 496a.
Likewise, the 9-pole wye-delta starter circuit diagram 498a depicted in
FIG. 49B includes three wye switching devices 500, 502, and 504, the
delta switching devices 506, 508, and 510, and three mains switching
devices 512a, 514a, and 516a. As shown in the depicted embodiments, the
mains switching devices 492a, 494a, 496a, 512a, 514a, and 516a are inside
the delta configuration. More specifically, the mains switching devices
492a, 494a, 496a, 512a, 514a, and 516a may be utilized as disconnect
switches to isolate the windings from the mains power when desired.

[0365] Other embodiments of the 8 and 9 pole wye-delta switching
arrangements are shown in FIGS. 49C and 49D, respectively. In particular,
the circuit diagram 480b depicted in FIG. 49C includes two wye switching
devices 482 and 484 and three delta switching devices 486, 488, and 490,
and three mains switching devices 492b, 494b, and 496b. Likewise, the
9-pole wye-delta starter circuit diagram 498b depicted in FIG. 49D
includes three wye switching devices 500, 502, and 504, the delta
switching devices 506, 508, and 510, and three mains switching devices
512b, 514b, and 516b. As shown in the depicted embodiments, the mains
switching devices 492b, 494b, 496a, 512b, 514b, and 516b are outside the
delta configuration. The mains switching devices 492b, 494b, 496a, 512b,
514b, and 516b may be used as disconnect switches to isolate the electric
motor 24 from the mains power.

[0366] Similar to the 5 and 6 pole wye-delta switching arrangements
discussed above, the 8 and 9 pole wye-delta switching arrangements may
perform the wye two-step start and the phase sequential wye-delta
switching, except that, before running through the openings and closings,
the mains switching devices may be closed to provide power to the
windings. In addition, the 8 and 9 single-pole switching arrangements may
or may not utilize POW techniques to execute the wye two-step start and
the phase sequential wye-delta sequencing. Also, the physical layout of
the various wye-delta switching arrangements may be highly configurable
due to the modularity enabled by utilizing single-pole switching devices,
which will be discussed in further detail below.

Motor Torque-Based Phase Sequential Switching

[0367] As noted above, a wye-delta starter (e.g., a 5-pole wye-delta
starter 374 or a 6-pole wye-delta starter 442) may supply electric power
to an electric motor 24 to run the motor 24 in a wye configuration or a
delta configuration. In should be noted that a 5-pole wye-delta starter
374 may be a special case of a 6-pole wye-delta starter 442. As such,
techniques applicable to a 5-pole wye-delta starter 374 may be easily
adaptable to a 6-pole wye-delta starter 44.

[0368] In some instances, when the electric motor 24 is run in wye, the
electric motor 24 may use less electric power to produce a first (e.g.,
lower) torque level, and when the electric motor 24 is run in delta, the
electric motor 24 may use more electric power to produce a second (e.g.,
higher) torque level. In other words, supplying electric power to the
electric motor 24 using a wye-delta starter 374 enables at least two
operating modes (e.g., less power consumption lower torque and more power
consumption higher torque).

[0369] However, there may be instances when it is desirable to operate the
motor 24 somewhere between the two operating modes. For example, it may
be desirable to produce more torque than produced when operating in wye,
but consume less electric power than consumed when operating in delta. In
contrast, it may be desirable to produce less torque than produced when
operating in delta, but consume more power than consumed when operating
in wye. Thus, the wye-delta starter may sequentially traverse through
mixed wye-delta configurations to increase or decrease the torque level
and/or power consumption as desired.

[0370] To help illustrate, FIGS. 50A-F describes configurations (e.g.,
open/close switching devices) of a 5-pole wye-delta starter 374 long with
corresponding torque levels produced by the electric motor 24. Turning to
FIG. 50A, when the second wye switching device 378 is closed, the
wye-delta starter 374 may provide two phases of electric power to the
motor windings 388 and 390. However, merely supplying two phases of
electric power may be insufficient to rotate the electric motor 24
because the resultant field cannot initiate rotation. As such, the
electric motor 24 may produce 0% of the motor's potential maximum torque
level (e.g., in the delta configuration) and consume minimal electric
power.

[0371] As shown in FIG. 50B, when first wye switching device 376 and
second wye switching device 378 are closed, the wye-delta starter 374 may
provide three-phase power to the motor windings 386, 388, and 390. More
specifically, in this configuration, the wye-delta starter 374 may supply
electric power to the electric motor 24 in a wye configuration. As such,
the motor 24 may produces less than or equal to 33% of the motor's
potential maximum torque level (e.g., in the delta configuration).
Additionally, in some embodiments, the power consumption of the electric
motor 24 may be less than or equal to 33% of the maximum power
consumption (e.g., in the delta configuration).

[0372] As shown in FIG. 50C, when first wye switching device 376 is opened
and second wye switching device 378 remains closed, the wye-delta starter
374 may again provide two phases of electric power to the motor windings
388 and 390 in a wye configuration. However, when the motor 24 has
already begun rotating, the two phases of electric power may be
sufficient to maintain rotation of the motor 24. As such, in this
configuration, the motor 24 may produce less than or equal to 22% of the
maximum torque level and power consumption may drop to less than or equal
to 22% of maximum power consumption.

[0373] As shown in FIG. 50D, when first delta switching device 380 is
closed and second wye switching device 378 remains closed, the wye-delta
starter 374 may provide three-phase electric power to the motor 24. More
specifically, the motor 24 may run in a mixed wye-delta configuration
with windings 388 and 390 connected in wye and first winding 386
connected in delta. As a result, the current waveforms may be unbalanced.
Nevertheless, in this configuration, the motor 24 may produce torque less
than or equal to 55% of the maximum torque level and the power
consumption may increases to less than or equal to 55% of the maximum
power consumption.

[0374] As shown in FIG. 50E, when third delta switching device 384 is
closed and switching devices 380 and 378 remain closed, the wye-delta
starter 374 may remain providing three-phase electric power to the motor
24. More specifically, the motor 24 may continue running in a mixed
wye-delta configuration with first winding 386 connected in delta, second
winding 388 connected in wye, and third winding 390 connected in both
delta and wye. As such, in this configuration, the motor 24 may produce
less than or equal to 66% of the maximum torque level and power
consumption may increase to less than or equal to 66% of the maximum
power consumption.

[0375] As shown in FIG. 50F, when second wye switching device 378 is open,
switching devices 380, 382, and 384 remain closed, the wye-delta starter
may provide three-phase electric power to the motor 24 in a delta
configuration. As such, in this configuration, the motor 24 may produce
less than or equal to 100% of the maximum torque level and power
consumption may increase to less than or equal to 100% of the maximum
power consumption. It should be noted that throughout the phase
sequential wye-delta switching steps, the torque is in the same direction
(e.g., positive).

[0376] Thus, as described above, the wye-delta starter 374 may facilitate
reducing strain on the motor 24 and/or a connected load 18 by gradually
adjusting torque, particularly when starting up the motor 24. To help
illustrate, a plot 518 of torque produced when starting up a motor 24
using sequential switching of a wye-delta starter is described in FIG.
50G. More specifically, a motor torque curve 519 describes torque
produced by the motor 24 between t0 and t7. In the depicted embodiment,
the wye-delta starter 374 may be disconnected between t0 and t1, in the
configuration described in FIG. 50A between t1 and t2, in the
configuration described in FIG. 50B between t2 and t3, in the
configuration described in FIG. 50C between t3 and t4, in the
configuration described in FIG. 50D between t4 and t5, in the
configuration described in FIG. 50E between t5 and t6, and in the
configuration described in FIG. 50F between t6 and t7.

[0377] Thus, as described by the motor torque curve 519, the motor 24 may
produce 0% of the motor's potential maximum torque level between t0 and
t1 since electric power is not supplied to the windings 386, 388, and
390. The motor 24 may continue producing 0% of the motor's potential
maximum torque level between t1 and t2. More specifically, as described
above, two phases of electric power are supplied to windings 388 and 390
in a wye configuration. However, the two phases may be insufficient to
initiate rotation of the motor 24.

[0378] As described by the motor torque curve 519, the motor 24 may begin
rotating and producing torque between t2 and t3. More specifically, as
described above, in this configuration the windings 386, 388, and 390 may
be connected in the wye configuration, thereby enabling the motor 24 to
produce less than or equal to 33% of the maximum torque level. In some
embodiments, connecting the windings 386, 388, and 390 in wye may be a
stable configuration. As such, the wye-delta starter 374 may remain in
this configuration for extended durations of time.

[0379] Additionally, as described by the motor torque curve 519, the motor
24 may continue rotating but produce a reduced amount of torque between
t3 and t4. More specifically, as described above, in this configuration
the windings 388 and 390 may remain connected in the wye configuration.
However, since the motor 24 is already in rotation, the two phases of
electric power supplied to windings 388 and 390 are sufficient to
maintain the rotation. In some embodiments, the rotation of the motor 24
may begin to slow when run in this configuration for an extended period.
As such, the wye-delta starter 374 may remain in this configuration for a
shorter duration.

[0380] Furthermore, as described by the motor torque curve 519, the motor
24 increase produced torque between t4 and t5. More specifically, as
described above, in this configuration windings 388 and 390 may remain
connected in wye and first winding 386 may be connected in delta, thereby
enabling the motor 24 to produce less than or equal to 55% of the maximum
torque level. In some embodiments, since electric power is supplied to
teach of the windings 386, 388, and 390, this mixed wye-delta
configuration may be a stable. As such, the wye-delta starter 374 may
remain in this configuration for extended durations of time.

[0381] As described by the motor torque curve 519, the motor 24 may again
increase produced torque between t5 and t6. More specifically, as
described above, in this configuration windings 388 may remain connected
in wye, first winding 386 may remain connected in delta, and third
winding 390 may be connected in both wye and delta, thereby enabling the
motor 24 to produce less than or equal to 66% of the maximum torque
level. In some embodiments, since electric power is supplied to teach of
the windings 386, 388, and 390, this mixed wye-delta configuration may be
a stable. As such, the wye-delta starter 374 may remain in this
configuration for extended durations of time.

[0382] Additionally, as described by the motor torque curve 519, the motor
24 may again increase produced torque between t6 and t7. More
specifically, as described above, in this configuration windings 386,
388, and 390 may each be connected delta, thereby enabling the motor 24
to produce less than or equal to 100% of the maximum torque level. In
some embodiments, connecting the windings 386, 388, and 390 in delta may
be a stable configuration. As such, the wye-delta starter 374 may remain
in this configuration for extended durations of time.

[0383] Thus, in the above described example, the wye-delta starter 374 may
utilize at least four intermediate torque levels to gradually ramp up the
motor 24. In fact, a number configurations used to produce the
intermediate torque levels may be stable. As such, in addition to merely
ramping up the motor 24, the wye-delta starter 374 may operate the motor
24 at multiple torque controlled configurations. For example, when less
than or equal to 55% of the maximum torque is desired, the wye-delta
starter 374 may close second wye switching device 378 and first delta
switching device 380.

[0384] As described above, power consumption of the motor 24 may correlate
with configuration of the wye-delta starter 374. For example, power
consumption may be greater when the connected in a delta configuration
than when connected in a wye configuration. As such, when desired torque
of the motor 24 capable of being produced by a lower stable
configuration, the wye-delta starter 374 may transition to a lower stable
state, thereby reducing power consumption.

[0385] In other words, the steps described above regarding phase
sequential wye-delta switching may be reversed (e.g., transition from
delta to an intermediate configuration) in order to reduce the amount of
torque produced and power consumed by the motor. That is, by reversing
the phase sequential wye-delta steps described, the torque and power
consumption may be stepped down. For example, while the motor is running
in delta configuration, the second delta switching device 382 may open
and the second wye switching device 378 may close. Accordingly, the motor
may be running in a mixed wye-delta configuration and the torque may
reduce to less than or equal to 66% of the maximum torque level and power
consumption may reduce to less than or equal to 66% of the maximum power
consumption. Similarly, the wye-delta starter 374 may transition to any
of the intermediate configurations (e.g., stable and less stable
intermediate configurations) to achieve the desired torque production and
power consumption.

[0386] Moreover, the stepwise motor torque and power consumption
progressive wye-delta phase sequential switching described above provides
various benefits to different applications. For example, a water pump may
use the disclosed techniques to slowly increase torque when switching
from wye to delta, thereby slowly increasing the amount of water
delivered to pipes, as opposed to turning the pump on full bore
immediately and blasting water through the pipes. This may increase the
lifespan of the pipes. In addition, it may be desirable to put certain
loads in a power save mode but still keep the motor running. Thus, if the
motor 24 is running in delta, it can reverse the sequential steps, as
mentioned above, and ramp down the amount of power consumed until a
desired amount is reached. As may be appreciated, the techniques
disclosed herein enable configuring the amount of torque produced and
power consumed by the motor 24 as desired by utilizing single-pole
devices (e.g., single-pole, single current-carrying path switching
devices 218) in a phase sequentially transition.

[0387] As such, the configuration of the motor starter (e.g., which
switching devices are open and which switching devices are closed) may be
based on a desired output torque level or a desired power consumption. As
such, one embodiment of a process 520 for determining configuration of
the switching devices in the motor starter based on a desired torque
level is shown in FIG. 51A. Generally, process 520 includes selecting a
desired torque level (process block 522), determining a configuration of
the motor starter based on the desired torque level (process block 524),
and setting the configuration (process block 526). In some embodiments,
the process 520 may be implemented via computer-readable instructions
stored in a non-transitory article of manufacture (e.g., the memory 226,
20, 46 and/or other memories) and executed via processor 224, 19, 45
and/or other control circuitry.

[0388] Accordingly, control circuitry 18 may determine the desired torque
level to be produced by the motor 24 (process block 522). More
specifically, in some embodiments, the desired torque level may be input
to the control circuitry 18 by a user. In other embodiments, the desired
torque level may be pre-configured in the control circuitry 18. For
example, certain loads may be started and the amount of torque produced
may be incrementally increased by the control circuitry 18 over a period
of time in order to gradually ramp up to 100% torque produced in delta.
Alternatively, it may be desirable to reduce the amount of torque a load
is producing if it has been running for a certain period of time, and,
thus, the control and monitoring circuitry 18 may select a reduced torque
level to produce.

[0389] In any embodiment, after the desired torque is determined, the
control and monitoring circuitry 18 may determine the configuration to
apply based upon the desired torque level (process block 524). As
described above with reference to FIGS. 50A-F, each step of the phase
sequential switching may produce a different amount of torque. For
example, when the motor is running in a wye configuration supplying
three-phase power to all three windings, less than or equal to 33% torque
may be produced (FIG. 50B). When the motor is running in a mixed
wye-delta configuration where two windings are in wye and one winding is
in delta, less than or equal to 55% torque may be produced (FIG. 50D).
Also, when one winding is in delta, one winding is in wye, and one
winding is in both wye and delta, less than or equal to 66% torque may be
produced (FIG. 50E), and when the motor is running in delta, less than or
equal to 100% torque may be produced (FIG. 50F). Thus, the control and
monitoring circuitry 18 may select the configuration that achieves the
desired torque level.

[0390] In alternative embodiments, if the desired torque is not exactly
one of the possible options, the control and monitoring circuitry may
determine which configuration most closely achieves the desired torque.
For example, the control and monitoring circuitry 18 may round the torque
up or down based on which available torque values are provided by the
different configurations. More specifically, if a user desires the
electric motor 24 to produce 40% torque and the two closest available
torque options are 33% and 55% torque production, the control and
monitoring circuitry 18 may round down to 33% because it is closer to 40%
than 55%. As a result, the control and monitoring circuitry 18 may select
the wye configuration depicted in FIG. 50B to apply to achieve the torque
closest to the desired 40% torque. Additionally or alternatively, the
control and monitoring circuitry 18 may round up to 55% torque to ensure
that sufficient torque is provided.

[0391] In further embodiments, the control and monitoring circuitry 18 may
periodically alternate between any two torque states to achieve the
desired (e.g., intermediate) torque level. More specifically, the
duration at each of the two torque states may adjust the resulting torque
level. For example, to produce a torque level of 60.5%, the control and
monitoring circuitry 18 may operate the wye-delta starter 374 in a first
mixed wye-delta configuration that produces 55% torque with a 50% duty
cycle and a second mixed wye-delta configuration that produce 66% torque
with a 50% duty cycle. In this manner, various intermediate torque levels
may be produced, which may be particularly useful for high inertia loads
like long conveyer lines and long sections of pipe (e.g., a water
hammer).

[0392] Once the configuration is determined, the control and monitoring
circuitry 18 may set the selected configuration by instructing the
switching devices to open or close to implement the determined
configuration (process block 526). It should be noted that in some
embodiments, determined configuration may be implemented with POW
techniques. As described above, utilizing POW techniques may prolong the
life span of the switching devices.

[0393] It should be further noted that, in some embodiments, the switching
devices may be opened or closed in accordance with the phase sequential
wye-delta switching. In other words, the control unit 18 may determine
the state (e.g., open or closed) of each of the switching device and
sequentially instruct each of the switching devices to open, close, or
maintain its current state. To help illustrate, if 55% torque level is
selected and the motor is started, the control and monitoring circuitry
18 may sequentially open and close the switching device, in accordance
with the phase sequential switching, to set the motor in the mixed
wye-delta configuration that achieves 55% torque level. Likewise, if the
motor is running in delta (e.g., 100% torque) and a lower torque is
selected, the control and monitoring circuitry 18 may determine and set a
different configuration by reverse the steps in the phase sequential
wye-delta switching. Additionally or alternatively, once the
configuration is determined, the control circuitry 18 may instruct the
switching devices to implement the configuration in any order, for
example, simultaneously.

[0394] Similarly, one embodiment of a process 530 for determining
configuration of the switching devices in the motor starter based on a
desired power consumption is shown in FIG. 51B. Generally, process 530
includes selecting a desired power consumption (process block 532),
determining a configuration of the motor starter based on the desired
power consumption (process block 534), and setting the configuration
(process block 536). In some embodiments, the process 530 may be
implemented via computer-readable instructions stored in a non-transitory
article of manufacture (e.g., the memory 226, 20, 46 and/or other
memories) and executed via processor 224, 19, 45 and/or other control
circuitry.

[0395] As can be appreciated, process 530 includes many of the same
processing steps as process 520. Specifically, the control circuitry 18
may determine a desired power consumption (process block 532). In some
embodiments, the control and monitoring circuitry 18 may select the power
consumption level based upon the type of load, pre-configured power modes
(e.g., power save mode), power consumption schedules, and so forth. For
example, the control circuitry 18 may determine amount of power
consumption based on the amount of power available. In other words, if
the control and monitoring circuitry 18 determine that a high amount of
power is available, the control and monitoring circuitry 18 may determine
that the maximum power consumption may be utilized. On the other hand, if
the control and monitoring circuitry 18 determine that a low amount of
power is available, the control and monitoring circuitry 18 may determine
that a power consumption less than the maximum should be utilized.

[0396] As described with reference to FIGS. 50A-F, each varying
configuration in the wye-delta starter may result in different power
consumptions. Thus, the control and monitoring circuitry 18 may determine
the motor configuration based upon the desired power consumption level
(process block 534). That is, the control and monitoring circuit 18 may
select the configuration (e.g., wye, mixed wye-delta, delta, etc.) that
consumes the desired amount of power. The control and monitoring
circuitry 18 may then instruct the switching devices to implement the
determined configuration.

[0397] Based on the above, the described techniques enables running a
wye-delta motor starter with varying torque levels and varying power
consumptions simply by opening and closing switching devices in the motor
starter.

Operator-Initiated Point-On-Wave Switching

[0398] As used in the various operations described herein, switching
device 218 may be used to selectively connect and/or disconnect electric
power from a load 14. For example, in a close operation, switching
devices 218 may be used to connect three-phase electric power to an
electric motor 24 in a manner that reduces electric arcing. More
specifically, as described above, two phases may be connected at a first
time in coordination with a predicted current zero-crossing and the third
phase may be connected based upon a subsequent predicted current
zero-crossing. In other words, the switching device 218 may close at
specific points on the electric power waveform.

[0399] In some embodiments, the various operations may be initiated by an
operator. For example, an operator may instruct the switchgear 16 to
connect electric power to the load 14 via a human-machine interface on
the control and monitoring circuitry 18. Accordingly, the operator
instruction may be received at any suitable time during operation via the
network 21. In other words, different operator instructions may be
received independent of the electric power to be connected or
disconnected from the load. Thus, to perform the operator initiated
operation at specific points on the electric power waveform, the control
and monitoring circuitry 18 may take into account the unpredictable
nature of when an operator instruction is received.

[0400] To help illustrate, FIG. 52 depicts a source voltage waveform 540
of one phase of electric power supplied by the power source 12 during an
operator-initiated make operation. As described above, an operator
instruction to make may be received independent from the source voltage
540. In other words, in the depicted embodiment, the operator instruction
may be received at some time before tR. To account for the unpredictable
timing of receiving the operator instruction, a reference point 542 in
the future may be selected. In the depicted embodiment, the reference
point 542 corresponds to a voltage zero-crossing (e.g., a predicted
current zero-crossing) at tR. In other embodiments, any suitable
reference point may be used.

[0401] From the reference point 542, the close operation may be performed.
More specifically, as described above, the processor 224 may determine
the expected make time 544 of the switching device 218. The processor 224
may determine a specific point 546 that is at least the expected make
time later than the reference point 542 to enable the switching device
218 to close at the specific point 546. Additionally, the processor 224
may determine when to apply the current profile (e.g., pull-in current)
to the operating coil 220 to make at the desired point 546 and instruct
the operating current to apply the current profile at the determined
time.

[0403] In some embodiments, the control and monitoring circuitry 18 may
receive the operator instruction via a human-machine interface, such as a
keyboard or a push button, at any suitable time during operation (process
block 550). More specifically, the operator instruction may contain an
instruction to perform a specific operation. For example, the operator
may instruct the wye-delta starter 374 to transition from wye to delta.
Accordingly, the control and monitoring circuitry 18 may determine what
operation to perform based on the operator instruction.

[0404] Additionally, as described above, the operation may be carried out
by making and/or breaking switching devices 218 at specific points on the
electric power waveform. Accordingly, the control and monitoring
circuitry 18 may determine the electric power waveforms based on sensor
measurement feedback (process block 552). More specifically, the control
and monitoring circuitry 18 may determine particular electric power
waveforms based on the operation that will be performed. For example,
when the operation is a make operation, the control and monitoring
circuitry 18 may determine the source voltage waveform. Additionally,
when the operation is a break operation, the control and monitoring
circuitry 18 may determine the current voltage waveform.

[0405] It should be noted that although the depicted embodiment depicts
that the electric power waveform is determined in response to the
operator instruction, additionally or alternatively, the control and
monitoring circuitry 18 may continuously determine the electric power
waveforms. In other words, the electric power waveforms may be determined
regardless of whether an operator instruction is received. For example,
the control and monitoring circuitry 18 may determine the source voltage
waveform and the source current waveform throughout operation. In some
embodiments, continuously determining the electric power waveforms may
enable diagnostics on the source 12, the switching device 218, the load
14, or any combination thereof.

[0406] On the electric power waveform, the control and monitoring
circuitry 18 may then select a reference point 542 in the future (process
block 554). As described above, the reference point may be used to
account for the unpredictable timing of the operator instruction.
Accordingly, in some embodiments, the reference point 542 may be selected
based on repeatable criteria to enable the operation to be initiated from
a predictable starting point. For example, the reference point 542 may be
selected from the future voltage zero-crossings on the electric power
waveform.

[0407] From the reference point, the control and monitoring circuitry 18
may initiate the operation (process block 556). More specifically, the
control and monitoring circuitry 18 may determine which switching device
218, and more specifically which operating coil driver circuitry 222,
will be used to carry out the operation. Additionally, the control and
monitoring circuitry 18 may determine the desired make times and/or
desired break times for each switching device 218. As described above,
the desired make times and desired break times may be specific points on
the electric power waveform. In other words, the control and monitoring
circuitry 18 may coordinate the switching of the various switching device
218 at specific points on a wave to perform the operation. As described
herein, examples of the operation may include closing switching devices
218, opening switching devices 218, transitioning from wye to delta,
transitioning from delta to wye, setting a specific torque or power
level, reversing an electric motor 24, or bypassing a load, such as a
motor drive.

[0408] It should be noted that there are certain asymmetrical edge
conditions that may be taken into consideration when attempting to break
ahead of a current zero-cross and/or when setting the electrical degree
separations of making and breaking the switching devices. For example, if
the selected reference point or amount of electrical degrees actually
causes an opening to occur after a current zero-crossing there may be
penalizing consequences. In fact, missing a current zero-crossing mark
when breaking may increase arcing because a half line cycle of increasing
current is applied during the opening in the switching device and the
stronger arc may prevent the switching device from opening. Thus, it may
be desirable to miss the mark short of the current zero-crossing and open
when the current is going downward on a half cycle to the current
zero-cross, as opposed to missing the mark after the current
zero-crossing.

[0409] Additionally or alternatively, the control and monitoring circuitry
18 may determine whether to perform process 548 based on the importance
of the operator instruction. For example, although the switching device
218 may break at specific points on a wave to reduce electric arcing, it
may be desirable to remove electric power from the load 14 as soon as
possible. In other words, the control and monitoring circuitry 18 may
determine the importance of the operator instruction and weigh the
importance against the consequences of performing the operation at any
point on the wave.

Synchronous Re-Closure

[0410] As described above, one or more switching devices 218 may be used
to connect and/or disconnect electric power from an electric motor 24.
For example, electric power may be connected to rotate the electric motor
24. Once the electric motor 24 is spinning, electric power may be
disconnected from the electric motor 24 for various reasons. Even though
electric power is removed, the momentum of the electric motor 24 and any
load actuated by the motor (e.g., a fan 47, a conveyer belt 48, or a pump
50) may keep rotating the electric motor 24 while friction begins to slow
the electric motor 24. As the electric motor 24 continues to rotate, a
back electromotive force (EMF) is generated. In other words, the electric
motor 24 acts as a generator to produce a voltage (e.g., back EMF) with a
changing frequency.

[0411] To restart the electric motor 24, electric power may be reconnected
to the electric motor 24. In some embodiments, it may be desirable to
restart the electric motor 24 as soon as possible. For example, if an
electric motor 24 in a chiller 54 completely stops, the gas and liquid
refrigerant in the chiller 54 may become displaced. Thus, to restart the
electric motor 24 may take an inconvenient period of time. Accordingly,
electric power may be reconnected while the electric motor 24 is still
rotating. As described above, the electric motor 24 generates a back EMF
with a changing frequency commensurate with it rotational frequency while
it is rotating. However, since the frequency is changing, the back EMF
and the electric power to be reconnected to electric motor 24 may be out
of phase. In some embodiments, when electric power is reconnected while
the electric power is lagging behind the back EMF, negative torque may be
generated in the electric motor 24, which may decrease the lifespan of
the motor and/or a connected load or result in surge currents that trip
protection circuitry.

[0412] Accordingly, one embodiment of the present disclosure describes a
method for synchronously re-closing (i.e., reconnecting) electric power
to an electric motor 24. More specifically, the method includes starting
a counter when either the source electric power or the back EMF crosses
zero volts (i.e., voltage zero-crossings) and stopping the counter at the
next subsequent voltage zero-crossing. Additionally, the method includes
monitoring the counter value trend to determine whether the source
electric power or the back EMF is leading. Furthermore, the method
includes reconnecting the source electric power while it is leading the
back EMF based at least in part on the counter value trend. More
specifically, the source electric power may be reconnected at or after a
local minimum in the counter value trend. In other words, the local
minimum in the counter value trend may indicate when the source electric
power switches from lagging to leading the back EMF. Thus, reconnecting
at or after a local minimum facilitates reconnecting the source electric
power when it is leading the back EMF, which reduces the chances of
producing negative torque when re-closing. Additionally, it may be
beneficial to begin using the counter to monitor voltage zero-crossings
as soon as the electric motor is disconnected to reduce the likelihood of
the electric power and the EMF from being 180.degree. out of phase when
re-closing.

[0413] To help illustrate, FIG. 54 is a plot that depicts the source
electric power voltage waveform 558 and the back EMF voltage waveform 560
for one phase. As can be appreciated, the waveforms for the other two
phases of three-phase electric power will be offset by 120 degrees. In
some embodiments, the waveforms may be determined based on measurements
gathered by sensors 22 that monitor voltage at the power source 12 and
sensors 22 that monitor voltage at the electric motor 24. Additionally,
FIG. 54 depicts the counter value 562.

[0414] As depicted, the source voltage 558 and the back EMF voltage 560
have different frequencies. Thus, over time, the source voltage 558 and
the back EMF voltage 560 will drift into and out of phase from one
another. For example, at t1, the source voltage 558 is leading the back
EMF voltage 560. As the phases drift past each other, at t4, the source
voltage 558 transitions from leading to lagging behind the back EMF
voltage 560. As used herein, "leading" is generally intended to describe
when one waveform is between 0 to 180 degrees ahead of a subsequent
waveform, and "lagging" is generally intended to describe when one
waveform is between 0 to 180 degrees behind a preceding waveform.

[0415] Thus, to facilitate reconnecting the source electric power when the
source voltage 558 is leading the back EMF voltage 560, the control and
monitoring circuitry 18 (e.g., processor 224) may determine when the
source voltage 558 transitions from lagging to leading. In some
embodiments, the control and monitoring circuitry 18 may utilize a
counter, such as a free running counter (FRC) included in the processor
224, to facilitate keeping track of the transitions.

[0416] More specifically, the counter may be started at either a source
voltage 558 zero-crossing or a back EMF voltage 560 zero-crossing. The
counter may continue counting until a subsequent voltage zero-crossing is
reached. For example, the source voltage 558 zero-crossing at t1 starts
the counter. As the counter runs, the counter value 562 continues to
increase. The counter stops at the next subsequent voltage zero-crossing,
which is the back EMF voltage 560 zero crossing at t2. After t2, the
counter value 562 is reset. Thus, the counter value 562 may be used to
indicate the time difference between adjacent voltage zero-crossings. In
other words, the counter value 562 at t2 indicates the lead the source
voltage 558 has over the back EMF voltage 560 (e.g., time difference
between t1 and t2). Since the frequency of the source voltage 558 is
higher than the back EMF voltage 560, the source voltage's lead over the
back EMF voltage 560 continues to increase. Accordingly, as depicted, the
trend of the counter value 562 is increasing when the source voltage 558
is leading.

[0417] It is noted that the counter may stop at any subsequent voltage
zero-crossing. For example, the source voltage 558 zero-crossing at t3
starts the counter and the counter value 562 increases until the
subsequent source voltage 558 zero-crossing at t4. In other words, the
counter is started and stopped by the same voltage waveform. Thus, the
counter value 562 at t4 is at a maximum and corresponds with half the
period of the source voltage 558 (e.g., 180 degrees). In other words, the
source voltage 558 is ahead of the back EMF voltage 560 by more than 180
degrees. Thus, based on the definitions above, the source voltage 558 has
transitioned to lagging behind the back EMF voltage 560. In other words,
a local maximum of the counter value 562 trend indicates the transition
of the source voltage 558 from leading to lagging behind the back EMF
voltage 560.

[0418] Accordingly, after t4, the source voltage 558 is lagging behind the
back EMF voltage 560. As described above, the frequency of the source
voltage 558 is higher than the back EMF voltage 560. In other words, the
source voltage 558 lag behind the back EMF voltage 560 continues to
decrease. Accordingly, as depicted, the trend of the counter value 562 is
decreasing when the source voltage 558 is lagging.

[0419] As the amount of lag continues to decrease, the source voltage 558
eventually overtakes the back EMF voltage 560 and transitions to leading
the back EMF voltage 560. Similar to the transition from leading to
lagging, the transition from lagging to leading may be based on the
counter value 562 trend. For example, minimum amount of lag occurs at t5.
Accordingly, as depicted, a first minimum counter value 562 occurs at t5.
Thus, the source voltage 558 will shortly thereafter transition to
leading the back EMF voltage 560. Additionally, as depicted, a second
minimum counter value 562 occurs at t6 because the source voltage 558 has
transitioned to slightly leading the back EMF voltage 560. In other
words, a local minimum of the counter value 562 trend indicates the
transition of the source voltage 558 from lagging to leading the back EMF
voltage 560.

[0420] Accordingly, the electric power may be reconnected to the electric
motor 24 when the source voltage 558 is leading the back EMF voltage 560
based at least in part on the counter value 562. One embodiment of a
process 564 for reconnecting electric power to the electric motor 24 is
shown in FIG. 55. Generally, the process 564 includes starting a counter
at a source voltage zero-crossing or a back EMF voltage zero-crossing
(process block 566), stopping the counter at the next source voltage
zero-crossing or back EMF voltage zero-crossing (process block 568),
monitoring the counter value trend (process block 570), and reconnecting
electric power after a local minimum in the counter value trend (process
block 572).

[0421] In some embodiments, the processor 224 included in the operating
coil driver circuitry 222 may be used to execute the process 564. As
described above, the counter used may be included in the processor 224.
Accordingly, the processor 224 may start the counter when it detects a
source voltage 558 zero-crossing or a back EMF voltage 560 zero-crossing
(process block 566). Additionally, the processor 224 may stop the counter
when it detects a next subsequent source voltage 558 zero-crossing or a
back EMF voltage 560 zero-crossing (process block 568). To facilitate
detecting the voltage zero-crossings, sensors 22 that monitor voltage at
the power source 12 and/or the electric motor 24 may feedback
measurements to enable the processor 224 to determine the source voltage
558 and the back EMF voltage 560.

[0422] Additionally the processor 224 may monitor the trend of the counter
value 562 (process block 570). More specifically, the processor 224 may
store the counter value 562 each time the counter stops, for example in
memory 226. Additionally, the processor 224 may store a time
corresponding with when each counter value 562 was stopped. Thus, the
processor 224 may determine the trend of the counter value 562 by looking
at the previously stored counter values 562. For example, in
chronological order, a first counter value, a second counter value, and a
third counter value may be stored. Thus, when the second counter value is
less than the first counter value and the third counter value, the
processor 224 may determine that a local minimum occurs at the time
corresponding with the second counter value. On the other hand, when the
second counter value is higher than the first counter value and the third
counter value, the processor 224 may determine that a local maximum
occurs at the time corresponding with the second counter value.

[0423] Based on the counter value 562 trend, electric power may be
reconnected after a local minimum (process block 572). As discussed
above, the processor 224 may determine when a local minimum occurs.
Accordingly, once the local minimum is detected, the processor 224 may
reconnect electric power to the electric motor 24. In some embodiments,
the processor 224 may instruct the operating coil driver circuitry 222 to
re-close the switching device 218, which may include setting the
operating coil current 250 to the pull-in current. More specifically,
once it is determined that the source voltage 558 is leading, the
processor 224 may execute process 258 to re-close the switching device
218 at a desired time to make, for example, based upon a predicted
current zero-crossing, as described above. Additionally or alternatively,
other means for reconnecting the electric power may be used, such as
insulated-gate bipolar transistors.

[0424] As described above, when the trend of the counter values 562 is
increasing, the source voltage 558 is leading the back EMF voltage 560.
Thus, if the switching device 218 is closed between t1 to t4, electric
power will be reconnected while the source voltage 558 is leading the
back EMF voltage 560. However, the amount the source voltage 558 leads
the back EMF voltage 560 may affect the increase in positive torque
generated in the electric motor 24 when electric power is reconnected.
Accordingly, to limit the positive torque produced, a threshold counter
value may be used. For example, if trend is increasing (e.g., after a
local minimum) and the counter value 562 is less than the threshold
value, the switching device 218 may be closed. On the other hand, if
counter value 562 is greater than the threshold value, the switching
device 218 may wait for a subsequent local minimum to close.

[0425] Additionally, as discussed in previous sections, the make operation
of the switching device 218 is generally not instantaneous. In other
words, the source voltage 558 may be leading the back EMF voltage 560 by
a larger amount than when the local minimum was detected. In most
embodiments, the amount of torque generated when the source voltage 558
leads the back EMF voltage 560 by between 0-90 degrees will not
negatively affect the electric motor 24. Accordingly, the threshold
counter value may be reduced to account for the delay.

[0426] Nevertheless, in some embodiments, the processor 224 may predict
when a local minimum in the counter value 562 will occur. More
specifically, the processor 224 may predict the next local minimum based
on the load actuated by the electric motor 24. For example, when the
electric motor 24 is actuating a pump 50, the electric motor 24 may slow
according to a square log curve. Thus, the processor 224 may determine
how the frequency of the back EMF voltage 560 generated by the motor will
change, which then may be used to predict when the next local minimum
will occur.

[0427] In fact, in some embodiments, the processor 224 may determine the
type of load the electric motor 24 is actuating based at least in part on
where the local minimums occur. For example, when the occurrence of the
local minimums quickly decreases, the processor 224 may determine that
the frequency of the back EMF voltage 560 is quickly decreasing. As such,
the processor 224 may determine the relative magnitude of the inertia of
a load.

[0428] As can be appreciated, the techniques described above may be
utilized for reconnecting multiple phases of electric power. For example,
process 564 may be executed with regard to each phase independently.
Additionally or alternatively, since each phase of the source voltage 558
and the back EMF voltage 560 will be proportionally offset (e.g., by 120
degrees) from one another, the counter may be utilized on a single phase.
More specifically, when the processor 224 determines that one phase of
the source voltage 558 is leading the back EMF voltage 560, the other
phases of the source voltage 558 will also be leading. Thus, in some
embodiments, each phase may be connected substantially simultaneously.
Accordingly, this may be useful in an open non-sequential wye-delta
starter. For example, after the wye connections open, the electric motor
24 will continue rotating. To close the delta connections, the processor
224 may determine when the source voltage 558 is leading the back EMF
voltage 560 by examining a single phase.

Switch-Based Detection of Motor Conditions

[0429] Utilizing the single-pole switching devices (e.g., single-pole,
single current-carrying path switching devices 218 described above) may
enable increasing the amount of control over the electric power supplied
to the electric motor 24. For example, the single-pole switching devices
may enable independently controlling each phase of supplied three-phase
power, which may enable detection of faults (e.g., a phase-to-ground
short or a phase-to-phase short) while minimizing duration of the faulty
condition and amount of energy present during the faulty condition. As
will be described in detail herein, in some embodiments, faults (e.g., a
short circuit) may be detected by applying a very brief, low voltage
pulse (e.g., lower than the line voltage) to the motor 24 at a point on
the sinusoidal waveform coordinated with a voltage zero-crossing. The
pulse may be applied for a minimal time sufficient for fault detection.
Thus, if a short circuit exists, the energy remains relatively small due
to the low voltage and short duration. As a result, the fault may be
cleared without tripping any connected circuit breakers, and be
detrimental to the electric motor 24 and its windings may be reduced.

[0430] Examples of faulty motor conditions that may be detected using the
disclosed techniques include a phase-to-ground short, a phase-to-phase
short, and a phase-to-phase open circuit, among others. A phase-to-ground
short may occur when the insulation to ground has deteriorated and
current flows into the ground, for example, in a winding of a motor. A
phase-to-phase short may occur when phases come into contact without any
load or resistance, such as when wires have been connected improperly
(e.g., two phases wired together), an external object has been laid
across the wires, two motor windings are shorted, and so forth.
Additionally, a phase-to-phase open circuit may occur when windings in a
motor are disconnected or otherwise open circuited.

[0431] To determine whether such faults exist, a technique referred to as
"sniffing," herein, may be employed. Generally, as will be described in
more detail below, sniffing may be defined as momentarily connecting a
phase of electrical power to test for a phase-to-ground short and/or
momentarily connecting two phases of electrical power to test for
phase-to-phase faults. Depending on the load being started, these
techniques may be performed before each start or may be performed
intermittently over a plurality of starts or during commissioning of a
new or revised installation.

[0432] The benefits of using the techniques before starting may extend the
lifespan of a load (e.g., electric motor 24) by supply power to the load
advantageous for protection circuitry to handle potential fault currents.
In fact, in some embodiments, different trip behavior may be used during
the sniffing process. For example, the protection circuitry may use a
higher protection scheme (e.g., more sensitive) when sniffing and return
to a normal protection scheme thereafter. In this manner, any results of
a possible fault detection during sniffing may be more effectively
mitigated by the protection circuitry.

[0433] With the foregoing in mind, FIG. 56A is a diagrammatical
representation of circuitry for detecting motor conditions utilizing
single-pole switching devices and a corresponding timing diagram,
respectively. Although single-pole, single current-carrying path
switching devices are described, any other type of switching device, such
as a three-phase offset pole switching device, may be used.

[0434] As depicted in the motor system 574, a power source 12 provides
three-phase electric power to an electric motor 24 via three single-pole
switching devices (576, 578, and 580), one for each phase. It should be
noted that the single-pole switching devices may include the single-pole,
single current path switching devices described above (e.g., contactors,
relays, etc.). Additionally or alternatively, single-pole, multiple
current-carrying path switching devices may be used. Each phase may be
connected to a separate winding on the motor 24 via separate motor
terminal. Further, the electric motor 24 may be connected to the ground
582.

[0435] In some embodiments, the operation (e.g., opening or closing) of
the single-pole switching devices may be controlled by control and
monitoring circuitry 18. In other words, the control and monitoring
circuitry 18 may instruct the single-pole switching devices (576, 578,
and 580) to connect or disconnect electric power. Additionally, as
depicted, the control and monitoring circuitry 18 may be remote from the
single-pole switching devices (576, 578, and 580). In other words, the
control and monitoring circuitry 18 may be communicatively coupled to the
single-pole switching devices (576, 578, and 580) via a network 21. In
some embodiments, the network 21 may utilize various communication
protocols such as DeviceNet, Profibus, or Ethernet. The network 21 may
also communicatively couple the control and monitoring circuitry 18 to
other parts of the system 574, such as other control circuitry or a
human-machine-interface (not depicted). Additionally or alternatively,
the control and monitoring circuitry 18 may be included in the
single-pole switching devices (576, 578, and 580) or directly coupled to
the single-pole switching devices, for example, via a serial cable.

[0436] Furthermore, as depicted, the electric power output from the
single-pole switching devices (576, 578, and 580) may be monitored by
sensors 22. More specifically, the sensors 22 may monitor (e.g., measure)
the characteristics (e.g., voltage or current) of the electric power.
Accordingly, the sensors 22 may include voltage sensors and current
sensors. Additionally, the characteristics of the electric power measured
by the sensors 22 may be communicated to the control and monitoring
circuitry 18 to generate waveforms (e.g., voltage waveforms or current
waveforms) that depict the electric power. The waveforms generated based
on the sensors 22 monitoring the electric power output from the
single-pole switching devices (576, 578, and 580) and supplied to the
motor 24 may be used in a feedback loop to, for example, monitor
conditions of the motor 24.

[0437] For example, the sensors 22 may sense whether current is flowing
when any of the single-pole switching devices (576, 578, and 580) close
and report this information to the control and monitoring circuitry 18.
If current is flowing, the control and monitoring circuitry 18 may then
determine how much current is flowing by generating a graph that analyzes
change in current (di) versus change in time (dt), which may be referred
to as the "di/dt slope." In some embodiments, the control and monitoring
circuitry 18 may look at the change in voltage (dv) versus change in time
(dt) to determine the current. As will be explained in detail below,
sensing whether current is flowing and determining the change in the
current (e.g., di/dt slope) may enable detecting whether a
phase-to-ground short or phase-to-phase fault is present.

[0438] Turning now to the operation of the sniffing process, which may be
utilized in some embodiments to detect phase-to-ground faults, the
control and monitoring circuitry 18 may utilize POW techniques to
determine a desired point on the waveform to close ahead of a voltage
zero-crossing. That is, each phase output by the power source 12, the
control and monitoring circuitry 18 may analyze the phase voltage to
determine when it will cross zero on the voltage waveform and pick a
desired point to close a few electrical degrees before that
zero-crossing. Then, the control and monitoring circuitry 18 may apply a
very brief, low line voltage pulse (e.g., lower than the line voltage) to
the motor 24 by closing the switching device at the desired point on the
wave and quickly (e.g., milliseconds) opening the single-pole switching
device. One reason to close a few electrical degrees ahead of a voltage
zero-crossing (e.g., on the downward slope of a positive half cycle on
the AC waveform) is so that the energy remains small if a short circuit
exists due to the low voltage and short duration of the closure. If there
is any current (e.g., not zero) sensed by the sensors 22, then a
phase-to-ground fault may be present because the ground has closed the
circuit and current is flowing. However, if there is zero current sensed
by the sensors 22, then there may not be a phase-to-ground fault present.

[0439] This process may be utilized to test each phase independently. For
example, the control and monitoring circuitry 18 may determine a desired
point on the phase A waveform to close ahead of a voltage zero-crossing
and then send a signal to the single-pole switching device 576 to close
accordingly. Very quickly thereafter (e.g., a few milliseconds), the
single-pole switching device 576 may be instructed to open by the control
and monitoring circuitry 18 and the control and monitoring circuit 18 may
be notified if current is sensed by the sensor 22. If a current is
sensed, this may indicate that a phase-to-ground short is present in the
motor system 574. More specifically, if any current (e.g., not zero) is
sensed by the sensors a short may be present in a winding of the motor 24
that receives phase A or an interconnect that carries phase A to the
motor 24.

[0440] Additionally, the control and monitoring circuitry 18 may determine
a desired point on the phase B waveform to close ahead of a voltage
zero-crossing and then sending a signal to the single-pole switching
device 578 to close accordingly. Very quickly thereafter (e.g., a few
milliseconds), the single-pole switching device 578 may be instructed to
open by the control and monitoring circuitry 18 and the control and
monitoring circuit 18 may be notified if current is sensed by the sensor
22. More specifically, if any current (e.g., not zero) is sensed by the
sensors a short may be present in a winding of the motor 24 that receives
phase B or an interconnect that carries phase B to the motor 24.

[0441] Furthermore, the control and monitoring circuitry 18 determine a
desired point on the phase C waveform to close ahead of a voltage
zero-crossing and then sending a signal to the single-pole switching
device 580 to close accordingly. Very quickly thereafter (e.g., a few
milliseconds), the single-pole switching device 580 may be instructed to
open by the control and monitoring circuitry 18 and the control and
monitoring circuit 18 may be notified if current is sensed by the sensor
22. More specifically, if any current (e.g., not zero) is sensed by the
sensors a short may be present in a winding of the motor 24 that receives
phase C or an interconnect that carries phase C to the motor 24.
Additionally, if a phase-to-ground fault is detected, it may be desirable
to delay starting the motor so that the fault may be remedied and
detriment to the motor, load, and/or power circuit may be inhibited.

[0442] To help illustrate, the duration of each switching device closing
and opening, FIG. 56B presents a timing diagram of the operations. As
depicted, the y-axis represents the voltage applied to the coil, and the
x-axis represents the amount of time in milliseconds. The graph shows all
three phases being briefly pulsed and tested consecutively. A first
phase-to-ground fault detection begins by closing the single-pole
switching device 576 at t1 and opening the single-pole switching device
576 at t2. As may be seen, the elapsed time that the single-pole
switching device 576 remained closed between t1 and t2 is very brief
(e.g., a few milliseconds). In other words, the switching device 576 is
pulsed to detect phase-to-ground shorts related to phase A.

[0443] Similarly, a second phase-to-ground fault detection begins by
closing the single-pole switching device 578 at t3 and opening the
single-pole switching device 578 at t4, which is a few milliseconds after
at t3. As such, the switching device 578 is pulse to detect
phase-to-ground shorts related to phase B. Additionally, a third
phase-to-ground fault detection begins by closing the single-pole
switching device 580 at t5 and opening the single-pole switching device
580 at t6, which is a few milliseconds after t5. As such, the switching
device 580 is pulsed to detect phase-to-ground shorts related to phase C.

[0444] As described above, a low amount of voltage applied briefly to the
motor system 574 during the phase-to-ground testing because the switching
devices 576-580 are closed near a voltage zero-crossing for each phase.
Accordingly, low voltage and brief duration may reduce likelihood of
circuit breakers tripping, as well as reduce detriments to the motor and
its windings in the instance that a phase-to ground short is present.

[0445] Additionally, as described above, the sniffing process may also be
utilized to detect phase-to-phase shorts utilizing the system 574 in FIG.
56A. For example, the control and monitoring circuitry 18 may close and
open a single-pole switching device that supplies a first phase of
electric power and a single-pole switching device that supplies a second
phase of electric power one after the other such that there is a brief
overlap between when single-pole switching devices are closed. More
specifically, the switching devices may be pulsed when at a
phase-to-phase predicted current zero-crossing. In some embodiments, a
phase-to-phase predicted current zero-crossing may occur phase-to-phase
voltage is at a maximum. In some embodiments, the single pole switching
devices arranged in a delta configuration of a wye-delta motor starter
may be used to detect for phase-to-phase shorts.

[0446] Based on the current measured by the sensors 22, the control and
monitoring circuitry 18 may determine if a phase-to-phase fault is
present. More specifically, if no current is sensed, a phase-to-phase
open circuit may be present in the motor system 574 and require
maintenance. On the other hand, if a current is sensed, the control and
monitoring circuitry 18 may determine and analyze the change in the
current (e.g., di/dt slope). More specifically, a nearly vertical (e.g.,
rapidly increasing) di/dt slope may indicate that a phase-to-phase short
is present. In some embodiments, the phase-to-phase short may be caused
by the interconnects being in contact without a load or the windings are
shorted. When a phase-to-phase short is present, the motor windings may
be inspected to check the wiring before starting. If the di/dt slope is
changing over time or has some angle to it, the control and monitoring
circuitry 18 may determine that there is no phase-to-phase fault present.

[0447] This process may be repeated for each phase-to-phase combination.
For example, the phase A and phase B single-pole switching devices may be
controlled as described above to determine whether a phase-to-phase fault
is present. Next, the phase B and phase C single-pole switching devices
may be controlled as described above to determine whether a
phase-to-phase fault is present. Last, the phase A and phase C
single-pole switching devices may be controlled as described above to
determine whether a phase-to-phase fault is present.

[0448] In some embodiments, the above described sniffing process may be
utilized to test for phase-to-ground and phase-to-phase faults in systems
with any number of phases. For example, in a system that is receiving
single phase electric power, phase-to-ground short testing may be
performed by briefly pulsing the switching device closed and opened and
measuring for current. In addition, in a system receiving two phase
electric power, phase-to-ground testing may be performed for both phases
by briefly pulsing the respective switching devices closed and measuring
for current. Further, phase-to-phase short testing may be performed by
briefly overlapping the closures of the switching devices providing the
two phase power and analyzing the di/dt slope.

[0449] Further, the above described sniffing process using single-pole
switching devices and POW techniques for both phase-to-ground and
phase-to-phase short detection may be combined into a thorough detection
sequence that may be executed prior to starting the electric motor 24.
One embodiment of a process 584 for the sniffing process is shown in FIG.
57, which is a block diagram of logic for detecting motor conditions. The
process 584 may be implemented via computer-readable instructions stored
in a non-transitory article of manufacture (e.g., the memory 226, 20, 46
and/or other memories) and executed via processor 224, 19, 45 and/or
other control circuitry. It should be noted that the depicted sequence of
the process 584 is not meant to be limiting, and is for illustrative
purposes. Indeed, any one of the process blocks may be rearranged and
performed in different order than the depicted embodiment.

[0450] In some embodiments, the sequence 584 may begin by testing for
phase-to-ground shorts; however, in other embodiments, the sequence 584
may begin by testing for phase-to-phase faults. As such, phase A may be
analyzed for a phase-to-ground short by closing the single-pole switching
device 576 at a desired point on the waveform ahead of a voltage
zero-crossing, opening the single-pole switching device 576 after a few
milliseconds, and measuring for current (process block 586). Next, in
process block 588, the control and monitoring circuitry 18 may perform
sniffing on phase B to detect whether a phase-to-ground short exists
(process block 588). That is, the single-pole switching device 578 may be
briefly pulsed closed ahead of a voltage zero-crossing. Then, the
single-pole switching device 578 may be opened after a few milliseconds,
and the current may be measured to determine whether current is flowing
to the ground. In process block 590, the control and monitoring circuitry
18 may perform sniffing on phase C to detect whether a phase-to-ground
short exists (process block 590).

[0451] If there is current sensed by the sensors 22 for any one of the
phases, a phase-to-ground short may be present, and a user may determine
how much current is present and decide whether to start the load (e.g.,
electric motor 24) or not. If there is no current sensed for any of the
phases during the phase-to-ground detection, or the user decides to
proceed with starting, the sequence 584 may move to testing for
phase-to-phase faults.

[0452] To test for phase-to-phase faults, the control and monitoring
circuitry 18 may utilize sniffing to detect whether there is a phase A to
phase B fault present (process block 592). Additionally, the control and
monitoring circuitry 18 may utilize sniffing to detect whether there is a
phase B to phase C fault present (process block 594) and utilize sniffing
to detect whether there is a phase A to phase C fault present (process
block 596). More specifically, if the di/dt slope indicates a
phase-to-phase fault is present, the user may decide to delay starting
until the condition is remedied. The combined sequence of phase-to-ground
short detecting process blocks 586-590 and the phase-to-phase short
detecting process blocks 592-596 may be executed as desired prior to
starting a load (e.g., electric motor 24), such as each time before the
load starts or on a periodic basis.

[0453] As previously mentioned, the benefits of performing the sequence
584, or a combination thereof, may reduce undesirable maintenance
conditions of the electric motor 24 and its windings and inhibit tripping
any connected devices through the use of single-pole switching devices
and POW techniques to detect faults using near minimal energy.

[0454] In an alternative embodiment, sniffing may be performed two
single-pole switching devices in series to detect phase-to-ground shorts
and/or phase-to-phase faults. It should be noted that the single-pole
switching devices may include the single-pole, single current-carrying
path switching devices 218. Additionally or alternatively, in some
embodiments, single-pole, multiple current-carrying path switching
devices may be used. The benefits of using two single-pole switching
devices in series is that it may enable a smaller more accurate time
window at which electric power is provided to the electric motor 24. FIG.
58A displays an embodiment of a motor system 598 that utilizes two
single-pole switching devices in series (576 & 600, 578 & 602, 580 &
604). More specifically, each pair of switching devices is used to supply
a single phase of electric power from the power source 12 to the electric
motor 24. Additionally, the electric motor 24 may be connected to ground
584.

[0455] As such, FIG. 58A is almost identical to FIG. 56A except for the
addition of the second set of single-pole switching devices 600, 602, and
604. In some embodiments, the second set of single-pole switching devices
600, 602, and may form a controllable disconnect switch. It should be
noted that the disclosed techniques are not limited to two switching
devices. Indeed, any number of single-pole switching devices may be
utilized. The two single-pole switching devices in series may detect
faults by briefly overlapping the closures so as to momentarily allow
closing of the circuit. Then, any current that is sensed by sensors 22
may be measured and analyzed by control and monitoring circuitry 18. For
example, a phase-to-ground short may be detected if any current is
detected by the sensors 22 when the circuit is briefly closed. Also, a
phase-to-phase short may be detected if the di/dt slope is nearly
vertical after syncing the overlapping closure of the two single-pole
switching devices in series for two phases.

[0456] Beginning with phase-to-ground short detection, it may be useful to
walk through how each pair of single-pole switching devices is utilized.
Specifically, with regards to phase A, the control and monitoring
circuitry 18 may utilize POW techniques to pick a desired point on the
sinusoidal waveform to close the first single-pole switching device 576
in the series ahead of a voltage zero-crossing and another desired point
to close the second single-pole switching device 600 ahead of the voltage
zero-crossing so that both single-pole switching devices' closures
overlap for some brief period of time (e.g., a couple milliseconds) prior
to the voltage zero-crossing. Further, the control and monitoring
circuitry 18 may also pick a desired point to open the single-pole
switching devices 576 ahead of the voltage zero-crossing and another
point to open the single-pole switching device 600. Then, the control and
monitoring circuitry 18 may pulse the single-pole switching devices 576
and 600 closed and opened based upon the desired points. In this way, the
overlapping closure of both single-pole switching devices may be
controlled so that the closure is opened before the voltage crosses zero.
Thus, the amount of energy present if there is a fault may be more
precisely controlled when two or more single-pole switching devices in
series. Also, the amount of time that the switching devices 576 and 600
are closed is minimal. As such, it should be noted that the switching
devices may be opened and close anywhere on the sinusoidal waveforms due
to the very brief amount of time that their closures overlap.

[0457] Accordingly, the control and monitoring circuitry 18 may determine
whether a phase-to-phase fault is present based on the current sensed by
the sensors 22. The above described phase-to-ground short detection
process utilizing two single-pole switching devices in series may be
repeated for both phase B and phase C using their respective single-pole
switching devices in series (578 & 602, 580 & 604).

[0458] The duration of the closure overlap may be better understood with
reference to FIG. 58B, which is a timing diagram of closing and opening
two single-pole switching devices in series. The y-axis represents the
voltage in the coil, and the x-axis represents time in milliseconds. Each
solid line and respective dotted line represent a pair of single-pole
switching devices in series applying voltage of a single phase to the
electric motor 24. For example, the control and monitoring circuitry 18
closes the first single-pole switching device 576 at t1 and closes the
second single-pole switching device 600 at t2. Additionally, the control
and monitoring circuitry 18 opens the first single-pole switching device
576 at t3 and opens the second single-pole switching device 600 at t4.
Accordingly, since both of the single-pole switching devices 576 and 600
are closed between t2 to t3, electric power is supplied to the electric
motor 24 between t2 to t3. This timeframe or window may be referred to as
the "closure overlap." The closure overlap may be only one or two
milliseconds long. Indeed, closing of the single-pole switching devices
576 and 600 may be intended to enable a controlled pulse of line voltage
to be applied that has insufficient energy to cause an undesirable
maintenance condition to the motor and/or its windings.

[0459] It is during the closure overlap that the current is measured to
detect phase-to-ground shorts. If any current is sensed by the sensors
22, there may be a phase-to-ground short present. In contrast, if no
current is sensed then there may not be a phase-to-ground short present.
As depicted, the timings of the closing and openings of the other pairs
of single-pole switching devices in series for phase B (t5-t8) and phase
C (t9-t12) may be similar. More specifically, as depicted, electric power
is applied between t6-t7 and between t10-t11. In other embodiments, the
phase-to-ground shorts may be tested in any desirable order. However, two
phases should not be tested simultaneously because if the closure
overlaps are synced current will be flowing and it may appear as though
there is a phase-to-ground fault when there is not.

[0460] To further illustrate the points on the sine wave that the two
single-pole switching devices in series may close and open, FIG. 59
depicts a graphical representation of timing for the motor condition
detection. The graph shows the voltage sine wave for a single phase of
electric power over time. For example, the sine wave may represent phase
A and the timings (t1-t4) represent the same single-pole switching device
closings and openings shown in FIG. 58B.

[0461] As described above, the first single-pole switching device 576 may
close at t1 and open at t3. Additionally, the second single-pole
switching device 600 may close at t2 and open at t4. Accordingly,
electric power may be applied to the electric motor 24 between t2 and t3,
which as depicted is slightly before the voltage zero crossing so that
the amount of energy available if a fault is present is low. That is, as
displayed, the voltage is only applied for a couple of milliseconds while
it is low before zero is crossed.

[0462] Similarly, the control and monitoring circuitry 18 may also detect
phase-to-phase faults utilizing the two single-pole switching devices in
series. For example, in some embodiments, the control and monitoring
circuitry 18 may pulse closed pairs of single-pole switching devices in
series such that electric power is connected for a brief period slightly
before a phase-to-phase predicted current zero-crossing. This may enable
brief closing of the circuit between phases to apply a small amount of
voltage for a few milliseconds so that if a fault exists, the fault may
be cleared quickly without causing an undesirable maintenance condition.
In addition, the brief closing of the circuit may enable the sensors 22
to sense any current that is flowing and the control and monitoring
circuitry 18 to analyze the di/dt slope of the current to determine
whether a phase-to-phase fault is present.

[0463] More specifically, the control and monitoring circuitry 18 may
utilize the two single-pole switching devices and POW techniques to
detect phase-to-phase faults between phase A to phase B, phase B to phase
C, and phase A to phase C, in any order. Taking phase A to phase B short
detection as an example, the control and monitoring circuitry 18 may
utilize POW techniques to pick points on phase A and phase B where a
phase-to-phase voltage maximum (e.g., a predicted current zero-crossing)
occurs. Additionally or alternatively, the phase-to-phase current and/or
voltage may be explicitly measured to determine when a current is
approaching between phases. For example, the voltage may be measured
between phase A and phase B, between phase B and phase C, and between
phase A and phase C to determine when to perform the sniffing for
phase-to-phase shorts. It is noted that the current conducted may be
asymmetrical. As such, it may be possible to determine other desirable
points to perform sniffing operations, for example, based at least in
part on characteristics of the load.

[0464] Next, the control and monitoring circuitry 18 may determine another
set of points on the phase A and phase B waveforms that are a few
electrical degrees prior to the predicted current zero-crossings to
ensure that a low current is applied when the circuit is closed. Then,
the control and monitoring circuitry 18 may pulse close and open the
pairs of single-pole switching devices for both phase A and phase B to
create closure overlaps that coincide (e.g., overlap briefly) between the
phases at the determined points before the predicted current
zero-crossing.

[0465] That is, the control and monitoring circuitry 18 may pulse close
the single-pole switching device 576 and then 600 at the desired point
before the predicted current zero-crossing to apply voltage for phase A,
while at nearly the same time, pulse close the single-pole switching
devices 578 and then 602 at the desired point before the predicted
current zero-crossing to apply voltage for phase B. Thus, both phases'
pairs of single-pole switching devices may create closure overlaps that
apply voltage for both phases at the same time in order to detect whether
there is a phase-to-phase fault. Quickly thereafter (e.g., milliseconds),
the single-pole switching device 576 supplying phase A and the
single-pole switching device 578 supplying phase B may be pulsed open
before the predicted current zero-crossing to break the circuit, thereby
opening the closure overlap.

[0466] As such, utilizing the single-pole switching devices in series
between phases in this manner may provide the benefit of generating a
more accurate pulse that is more precise in both amount of current
applied and the duration of current application in relation to the
predicted current zero-crossing. As a result, the controlled pulse of
line voltage applied may be insufficient to cause an undesirable
maintenance condition and/or trip connected devices (e.g., feeder circuit
breaker) if a short is present. Further, if a short is detected the
electric motor 24 may not be started so that the problem may be remedied
and detriments inhibited.

[0467] In some embodiments, the above described sniffing process utilizing
two switching devices in series may be utilized to test for
phase-to-ground and phase-to-phase faults in systems with any number of
phases. For example, in a system that is receiving single phase electric
power, phase-to-ground short testing may be performed by briefly
overlapping the closure of the two switching devices in series and
measuring for current. In addition, in a system receiving two phase
electric power, phase-to-ground testing may be performed for each
individual phase by briefly overlapping the closures of the switching
devices in series for that particular phase and measuring for current.
Further, phase-to-phase short testing may be performed for a system
receiving two phase power by briefly overlapping the closures of the
switching devices in series for both phases and analyzing the di/dt
slope.

[0468] Accordingly, utilizing the sniffing techniques described above may
enable controlling the amount and duration of electric power applied to a
motor. As such, potential undesirable maintenance conditions that may
occur when a fault is present may be reduced and protection circuitry may
not trip if a fault is present. More specifically, in the event of a
short circuit, the fault current may be much smaller than when closing at
full voltage, and the very brief pulse may easily clear the fault
current. Thus, expensive repairs may be reduced, equipment up time may be
increased, and operator safety may be improved.

Modular System Constructions

[0469] There are multiple configurations of devices enabled to meet
desired needs by leveraging the techniques described herein.
Specifically, the electromechanical single-pole switching devices
described above, such as the single-pole, single current-carrying path
switching devices 218, provide modularity that enables highly
configurable devices. Further, the mechanical interlock described above
enhances device configurability by preventing a particular switching
device from closing when an interlocked switching device is closed, which
may inhibit shorts. One such modular device that utilizes the techniques
described herein is the wye-delta starter described above. Indeed, in the
embodiments described below, 5-pole, 6-pole, 8-pole, and 9-pole wye-delta
starters are enabled utilizing electromechanical single-pole switching
devices (e.g., single-pole, single current-carrying path switching
devices) in conjunction with the mechanical interlock. It should be noted
that the number of poles may correspond to the number of single-pole
switching devices utilized in the configuration. In general, using the
single-pole switching devices in the described wye-delta starter
embodiments may result in devices having a compact size, which may save a
user money due to less hardware utilized and less complex wiring, and a
lower thermal footprint, which may improve ability to package such a
device in a smaller electrical enclosure with a smaller factory
footprint.

[0470] To help illustrate, one embodiment of a polyphase 5-pole wye-delta
starter 374 is shown in FIG. 60. As depicted, the 5-pole wye-delta
starter 374 includes five single-pole switching devices 376, 378, 380,
382, and 384, which may be electromechanical single-pole, single
current-carrying path switching devices. Additionally or alternatively,
the switching devices 376, 378, 380, 382, and 384 may include
single-pole, multiple current-carrying path switching devices.
Specifically, the 5-pole wye-delta starter 374 includes two wye switching
devices 376 and 378 and three delta switching devices 380, 382, and 384.
The switching devices are coupled to three-phase power from three mains
lines 392, 394, and 396, and are further coupled to three motor windings
386, 388, and 390. An advantage provided by using the single-pole, single
current-carrying path switching devices instead of switches arranged on a
common switch carrier is the number of power poles may be reduced (e.g.,
fewer switching devices). For example, the 5-pole wye-delta switching
device utilizes two wye switching devices (376 and 378) instead of three.

[0471] As depicted, the first delta switching device 380 and the first wye
switching device 376 are mechanically coupled via a first interlock 608,
and the second delta switching device 382 and the second wye switching
device 378 are mechanically coupled via a second interlock 610. It should
be noted that the first interlock 608 and second interlock 610 may be the
mechanical interlock described above. As such, only one of the first
delta switching device 380 and the first wye switching device 376 may be
closed at a time. Similarly, only one of the second delta switching
device 382 and the second wye switching device 378 may be closed at a
time. In addition, operation of the wye-delta starter 374 may be
controlled by the control and monitoring circuitry 18.

[0472] Additionally, as depicted, the output of first delta switching
device 380 and the output of first wye switching device 376 are
electrically coupled via a first interconnection 628. Similarly, the
output of second delta switching device 382 and the output of second wye
switching device 378 are electrically coupled via a second
interconnection 624. Furthermore, the output of third delta switching
device 384, the input of first wye switching device 376, and the input of
first delta switching device 380 are electrically coupled via a third
interconnection 620.

[0473] In the operation, the wye-delta starter 374 may receive a signal to
start the motor. Using the techniques above, the wye-delta starter 374
may initially execute a wye two-step start and then phase sequential
wye-delta switching. Both processes may include the control and
monitoring circuitry 18 opening and/or closing specified switching
devices in a sequential order so as to minimize negative torque, current
spikes, and oscillation magnitudes. As such, the wye two-step start may
be initiated by the second wye switching device 378 closing. Thus, a
first phase of electric power (e.g., phase A) is connected from the mains
line 394 to the motor second winding 388 and a second phase of electric
power (e.g., phase B) may be connected from the mains line 396 to the
third winding 390. During the second step of the wye two-step start, the
second first wye switching device 376 closes and a third phase of
electric power (e.g., phase C) is connected from the mains line 392 to
the first winding 386 of the electric motor 24. Thus, when the wye
switching devices 376 and 378 are the only switching devices closed in
the wye-delta starter 374, the motor is running in a wye configuration.

[0474] When initiated, the wye-delta starter 374 may execute the phase
sequential wye-delta switching. As such, the switching may begin by
opening the first wye switching device 376. As a result of breaking first
wye switching device 376, the motor windings 388 and 390 are being
supplied power. Next, the first delta switching device 380 may be closed,
resulting in first winding 386 being connected line 394 to line 392.
Windings 388 and 390 are still connected line 394 to line 396. As a
result of first delta switching device 380 closing, the windings 386,
388, and 390 are receiving three-phase unbalanced power due to the motor
running in a mixed wye-delta configuration. Then, the second wye
switching device 378 may be opened as the third step in the phase
sequential wye-delta transition. As a result, only motor first winding
386 is receiving power and the electric motor 24 is single phasing.
Further, the second delta switching device 382 may be closed after the
opening of the second wye switching device 378, thereby providing power
to second winding 388 in addition to 386. Last, the third delta switching
device 384 may be closed in order to complete the delta configuration.
Thus, three-phase power may be supplied via lines 392, 394, and 396 to
the motor windings 386, 388, and 390 in a delta configuration.

[0475] As previously discussed, in some embodiments, the 5-pole wye-delta
starter 374 may be implemented with single-pole, single current-carrying
path switching devices 218, as depicted in FIG. 61. More specifically, as
depicted, the mains line 394 is electrically coupled to input terminal
612 of the first delta switching device 380, the mains line 396 is
electrically coupled to input terminal 614 of the second delta switching
device 382, and the mains line 392 is electrically coupled to input
terminal 616 of the third delta switching device 384.

[0476] Additionally, the output terminal 626 of the first delta switching
device 380 and the output terminal of the first wye switching device 376
are electrically coupled by the first interconnect 628 (e.g., a first bus
bar). Similarly, the output terminal 632 of the second delta switching
device 382 and the output terminal 636 of the second wye switching device
378 are electrically coupled by the second interconnect 634 (e.g., a
second bus bar). Furthermore, the input terminal 618 of the first wye
switching device 376, the input terminal 622 of the second wye switching
device 378, and the output terminal 624 of the third delta switching
device 384 are electrically coupled by the third interconnect 620 (e.g.,
a third bus bar).

[0477] Thus, the first winding 386 may be electrically coupled to either
output terminal 626, output terminal 630, or the first interconnect 628.
Additionally, the second winding 388 may be electrically coupled to
either output terminal 632, output terminal 624, or the second
interconnect 634. Furthermore, the third winding 390 may be electrically
coupled to either input terminal 618, input terminal 622, or output
terminal 624.

[0478] Additionally, as depicted, the first delta switching device 380 and
the first wye switching device 376 are mechanically coupled by the first
interlock 608. Similarly, second delta switching device 382 and second
wye switching device 378 are mechanically coupled by the second interlock
610. It should be noted that the first interlock 608 and second interlock
610 may be the mechanical interlock described above.

[0479] In another embodiment, a polyphase 6-pole wye-delta starter 442 is
enabled utilizing six switching devices, as shown in FIG. 62. As with the
5-pole wye-delta starter, the switching devices may be electromechanical
single-pole, single current-carrying path switching devices independently
operated by the control and monitoring circuitry 18. Additionally or
alternatively, the switching devices may be single-pole, multiple current
carrying path switching devices. As depicted, the configuration of the
switching devices is almost identical as the 5-pole wye-delta starter
except another wye switching device is included in this embodiment.
Indeed, the 6-pole wye-delta starter 442 includes six switching devices
444, 446, 448, 450, 452, and 454. Specifically, the 6-pole wye-delta
starter 442 includes three wye switching devices 444, 446, and 448 and
three delta switching devices 450, 452, and 454.

[0480] The switching devices are coupled to three-phase power from three
mains lines 462, 464, and 466, and are further coupled to three motor
windings 456, 458, and 460. As discussed above, the 6-pole wye-delta
starter 442 may be controlled by the control and monitoring circuitry 18
to keep track of which switching devices open and/or close first during a
start and select a different switching device to open and/or close during
the next start. In this way, the control and monitoring circuitry 18 may
evenly distribute the number of switching operations each switching
device performs, which may increase the lifespan of the switching
devices.

[0481] As depicted, the first delta switching device 450 and the wye
switching 444 are coupled via a first interlock 638, the second delta
switching device 452 and the second wye switching device 446 are coupled
via a second interlock 640, and the third delta switching device 454 and
the third wye switching device 448 are coupled via a third interlock 642.
It should be noted that the interlocks 638, 640, and 642 may be the
mechanical interlocks described above. As such, only one of the first
delta switching device 450 and the first wye switching device 444 may be
closed at a time, only one of the second delta switching device 452 and
the second wye switching device 446 may be closed at a time, and only one
of the third delta switching device 454 and the third wye switching
device 448 may be closed at a time.

[0482] Additionally, as depicted, the output of first delta switching
device 450 and the output of first wye switching device 444 are
electrically coupled via a first interconnection 660. Similarly, the
output of second delta switching device 452 and the output of second wye
switching device 446 are electrically coupled via a second
interconnection 666, and the output of third delta switching device 454
and the output of third wye switching device 448 are electrically coupled
via a third interconnection 672. Furthermore, the input of first wye
switching device 444, the input of second wye switching device 446, and
the input of third wye switching device 448 are electrically coupled via
a fourth interconnection 665.

[0483] The steps in the wye two-step start and the phase sequential
wye-delta switching using six switching devices are essentially the same
as using five switching devices, which was described with reference to
FIG. 60. However, in the circuit diagram 442 depicted in FIG. 62 there
are three wye switching devices (444, 446, and 448), as opposed to two in
FIG. 60. Thus, the order in which the wye switching devices are closed in
the wye two-step start may change, and the order in which the wye
switching devices are opened in the phase sequential wye-delta switching
may change. In particular, regarding the wye two-step start, in order to
provide current to the windings using three wye switching devices, one of
the steps may close two wye switching devices simultaneously and the
other step may close the third switching device. For example, the wye
switching devices 446 and 448 may close simultaneously to connect
windings 458 and 460 from line 464 to line 466. Then, in the second step,
the third first wye switching device 444 may close in order to complete
the wye configuration. If POW techniques are utilized, these closures may
occur at desired points on the sinusoidal waveforms as determined by the
control and monitoring circuitry 18.

[0484] Once the electric motor 24 is running in wye configuration and the
winding current waveforms have reached steady state, the phase sequential
switching to delta may initiate. Alternatively, the phase sequential
switching to delta may initiate any point after the motor is set in the
wye configuration. As with the phase sequential wye-delta switching
utilizing a 5-pole wye-delta starter, in one embodiment, the first step
in the sequence utilizing a 6-pole wye-delta starter may include opening
one of the wye switching devices 444. Next, the switching device 450 may
be closed to connect first winding 456 in delta. After switching device
450 closes, the motor is running in a mixed wye-delta configuration with
first winding 456 in delta and windings 458 and 460 in wye. Then, the
remaining two closed wye switching devices 446 and 448 may be opened
simultaneously and the electric motor 24 may be single phasing (e.g.,
phase A) with only first winding 456 connected line 462 to line 464. The
switching devices 452 and 454 may be closed following the closure of the
switching device 450 either one after the other or simultaneously. As a
result, the windings 456, 458, and 460 are receiving three-phase electric
power and the electric motor is running in a delta configuration.

[0485] As previously discussed, in some embodiments, the 6-pole wye-delta
starter 442 may be implemented with single-pole, single current-carrying
path switching devices 218, as depicted in FIG. 63. More specifically, as
depicted, the mains line 464 is electrically coupled to input terminal
644 of first delta switching device 450, the mains line 466 is
electrically coupled to input terminal 646 of second delta switching
device 452, and the mains line 462 is electrically coupled to input
terminal 648 of third delta switching device 454.

[0486] Additionally, the output terminal 658 of first delta switching
device 450 and the output terminal 662 of the first wye switching device
444 are electrically coupled by the first interconnect 660 (e.g., a first
bus bar). Similarly, the output terminal 664 of the second delta
switching device 452 and the output terminal 668 of the second wye
switching device 446 are electrically coupled by the second interconnect
666 (e.g., a second bus bar), and the output terminal 670 of the third
delta switching device 454 and the output terminal of the third wye
switching device 448 are electrically coupled by the third interconnect
672 (e.g., a third bus bar. Furthermore, the input terminal 650 of the
first wye switching device 444, the input terminal 654 of the second wye
switching device 446, and the input terminal 656 of the third wye
switching device 448 are electrically coupled by the fourth interconnect
665 (e.g., a fourth bus bar).

[0487] Thus, the first winding 456 may be electrically coupled to either
output terminal 658, output terminal 662, or the first interconnect 660.
Additionally, the second winding 458 may be electrically coupled to
either output terminal 664, output terminal 668, or the second
interconnect 666. Furthermore, the third winding 460 may be electrically
coupled to either output terminal 670, output terminal 674, or the third
interconnect 672.

[0488] Additionally, as depicted, the first delta switching device 450 and
the first wye switching device 444 are mechanically coupled by the first
interlock 638. Similarly, the second delta switching device 452 and the
second wye switching device 446 are mechanically coupled by the second
interlock 640. Furthermore, the third delta switching device 454 and the
third wye switching device 448 are mechanically coupled by the third
interlock 642. It should be noted that the interlocks 638, 640, and 642
may each be the mechanical interlock described above.

[0489] In another embodiment, the polyphase 5-pole wye-delta starter may
be modified to isolate the motor windings by adding three mains lines
switching devices, which results in the polyphase 8-pole wye-delta
starter 676 shown in FIG. 64. As with the 5-pole wye-delta starter, the
switching devices may be electromechanical single-pole, single
current-carrying path switching devices independently operated by the
control and monitoring circuitry 18. Additionally or alternatively, the
switching devices may be single-pole, multiple current carrying path
switching devices. Independent operation enables making/breaking at
different times and in different orders. As depicted, the configuration
of the switching devices is identical to the 5-pole wye-delta starter
except for the addition of three mains lines switching devices in the
8-pole wye-delta starter embodiment. The 8-pole wye-delta starter 676
includes eight switching devices 678, 680, 682, 686, 688, 690, 692, and
694.

[0490] Specifically, the 8-pole wye-delta starter 676 includes two wye
switching devices 678 and 680, three delta switching devices 682, 684,
and 686, and three mains lines switching devices 688, 690, and 692. The
three mains lines switching devices 688, 690, and 692 are electrically
coupled to three-phase power from three mains lines 694, 696, and 698 and
are further coupled to three motor windings 700, 702, and 704 and the
delta switching devices 682, 684, and 686. The delta switching devices
682, 684, and 686 are also electrically coupled to the wye switching
devices 678 and 680 and the windings 700, 702, and 704. An advantage of
utilizing the mains line switching devices 688, 690, and 692 is that they
may be utilized as disconnects in order to protect the electric motor 24
from undesirable maintenance by faulty conditions or the like.
Additionally, utilizing the mains lines switching devices 688, 690, and
692 may enable testing condition of the electric motor 24 before
performing a start. For example, as discussed above, phase-to-ground and
phase-to-phase shorts may be tested using the mains lines switching
devices. Further, the mains lines switching devices may act as
disconnects in case a short is present or the windings need to be
isolated from the mains power.

[0491] As depicted, the first delta switching device 682 and the first wye
switching device 678 are coupled via a first interlock 706, and the
second delta switching device 684 and the second wye switching device 680
are coupled via a second interlock 708. It should be noted that the
interlocks 706 and 708 may be the mechanical interlocks described above.
As such, only one of the first delta switching device 682 and the first
wye switching device 678 may be closed at a time, and only one of the
second delta switching device 684 and the second wye switching device 680
may be closed at a time.

[0492] Additionally, as depicted, the output of first delta switching
device 682 and the output of first wye switching device 678 are
electrically coupled via a first interconnection 738. Similarly, the
output of the second delta switching device 684 and the output of second
wye switching device 680 are electrically coupled via a second
interconnection 744. Furthermore, the input of the first wye switching
device 678, the input of the second wye switching device 680, and the
output of the third delta switching device 686 are electrically coupled
via a third interconnection 732.

[0493] The steps in the wye two-step start and the phase sequential
wye-delta switching using eight switching devices are essentially the
same as using five switching devices. However, in the circuit diagram 676
depicted in FIG. 64 there are three mains lines switching devices (694,
696, and 698) that are isolating the windings (700, 702, and 704). Thus,
when a signal to start the motor is received by the 8-pole wye-delta
starter, the mains line switching devices (688, 690, and 692) may close
prior to running the wye two-step start and the phase sequential
wye-delta switching. After the mains line switching devices are closed,
the wye two-step start and the phase sequential wye-delta switching may
be executed the same as the 5-pole wye-delta starter.

[0494] Specifically, the wye two-step start may begin by the second wye
switching device 680 closing. Thus, windings 702 and 704 may be receiving
power from line 696 to line 698. During the second step of the wye
two-step start the first wye switching device 678 closes and a third
phase of electric power (e.g., phase C) is connected from the mains line
694 to the first winding 700 of the electric motor 24. Thus, when the wye
switching devices 678 and 680 and the mains line switching devices 688,
690, and 692 are the only switching devices in the 8-pole wye-delta
starter 676 that are closed, the motor is running in a wye configuration.

[0495] When initiated, the 8-pole wye-delta starter 676 may execute phase
sequential wye-delta switching. As such, the transition may begin by
opening the first wye switching device 678. As a result of breaking
switching device 678, only motor windings 702 and 704 are being supplied
power. Next, the first delta switching device 682 may be closed,
resulting in first winding 700 being connected line 696 to line 694 in
delta. Windings 702 and 704 are still connected line 696 to line 698 in
wye. Thus, as a result of the first delta switching device 682 closing,
the windings 700, 702, and 704 are receiving three-phase unbalanced power
due to the motor running in a mixed wye-delta configuration. Then, the
second wye switching device 680 may be opened as the third step in the
phase sequential wye-delta transition. As a result, only motor first
winding 700 is receiving power and the electric motor 24 is single
phasing. Further, the second delta switching device 684 may be closed
after the opening of the second wye switching device 680, thereby
providing power to second winding 702 in addition to 700.

[0496] The third delta switching device 686 may then be closed in order to
complete the delta configuration. Thus, three-phase power being may be
supplied via lines 694, 696, and 698 to the motor windings 700, 702, and
704 in a delta configuration. However, if at any time the control and
monitoring circuitry 18 determines that power needs to be cut off from
the electric motor 24, the mains line switching devices (688, 690, and
692) may be signaled to open one at a time or all at once. If POW
techniques are utilized the openings may be ahead of current
zero-crossings.

[0497] In some embodiments, the 8-pole wye-delta starter 676 may be
implemented with single-pole, single current-carrying path switching
devices 218, as depicted in FIG. 65. More specifically, as depicted, the
first mains line 696 is electrically coupled to input terminal 712 of the
first mains line switching device 690, the second mains line 698 is
electrically coupled to input terminal 714 of the second mains line
switching device 692, and the third mains line 694 is electrically
coupled to input terminal 710 of the third mains line switching device
688. The output terminal 716 of the third mains line switching device 688
is electrically coupled to the input terminal 718 of the third delta
switching device 682, the output terminal 720 of the first mains line
switching device 690 is electrically coupled to the input terminal 722 of
the first delta switching device 682, and the output terminal 724 of the
second mains line switching device 692 is electrically coupled to the
input terminal 726 of the second delta switching device 684.

[0498] Additionally, the output terminal 736 of first delta switching
device 682 and the output terminal 740 of the first wye switching device
678 are electrically coupled by the first interconnect 738 (e.g., a first
bus bar). Similarly, the output terminal 742 of the second delta
switching device 684 and the output terminal 746 of the second wye
switching device 680 are electrically coupled by the second interconnect
744 (e.g., a second bus bar). Furthermore, the input terminal 728 of the
first wye switching device 678, the input terminal 730 of the second wye
switching device 746, and the output terminal 734 of the third delta
switching device 686 are electrically coupled by the third interconnect
732 (e.g., a third bus bar).

[0499] Thus, the first winding 700 may be electrically coupled to either
output terminal 736, output terminal 740, or the first interconnect 738.
Additionally, the second winding 702 may be electrically coupled to
either output terminal 742, output terminal 746, or the second
interconnect 744. Furthermore, the third winding 704 may be electrically
coupled to either output terminal 734, input terminal 728, input terminal
730, or the third interconnect 732

[0500] Additionally, as depicted, the first delta switching device 682 and
the first wye switching device 678 are mechanically coupled by the first
interlock 706. Similarly, the second delta switching device 684 and the
second wye switching device 680 are mechanically coupled by the second
interlock 702. It should be noted that the interlocks 702 and 706 may
each be the mechanical interlock described above.

[0501] In another embodiment, the polyphase 6-pole wye-delta starter may
be modified to isolate the motor windings by adding three mains line
switching devices, which results in the polyphase 9-pole wye-delta
starter 748 shown in FIG. 66. As with the 6-pole wye-delta starter, the
switching devices may be electromechanical single-pole, single
current-carrying path switching devices independently operated by the
control and monitoring circuitry 18. Additionally or alternatively, the
switching devices may include single-pole, multiple current carrying path
switching devices. Independently operating the switching devices enables
making/breaking at different times and in different orders. Further, the
9-pole wye-delta starter 748 may be enabled with or without POW
techniques. As depicted, the configuration of the switching devices is
almost identical as the 6-pole wye-delta starter except for the addition
of three mains line switching devices in the 9-pole wye-delta starter
embodiment. As such, the 9-pole wye-delta starter 748 includes nine
switching devices 750, 752, 754, 756, 758, 760, 762, 764, and 766.

[0502] Specifically, the 9-pole wye-delta starter 748 includes three wye
switching devices 750, 752, and 754, three delta switching devices 756,
758, and 760, and three mains line switching devices 762, 764, and 766.
The three mains line switching devices are electrically coupled to
three-phase power from three mains lines 768, 770, and 772 and are
further electrically coupled to three motor windings 774, 776, and 778
and the delta switching devices 756, 758, and 760. The delta switching
devices 756, 758, and 760 are also electrically coupled to the wye
switching devices 750, 752, and 754 and the windings 774, 776, and 778.
An advantage of utilizing the mains line switching devices 762, 764, and
766, is that they may be utilized as disconnects in order to protect the
electric motor 24 from undesirable maintenance by faulty conditions or
the like. By acting as a gatekeeper to the mains power, the mains line
switching devices 762, 764, and 766 are able to isolate the windings 774,
776, and 778. Further, in some embodiments, the mains line switching
devices 762, 764, and 766 may be utilized to test for phase-to-ground and
phase-to-phase shorts before starting the motor.

[0503] As depicted, the first delta switching device 756 and the wye
switching 750 are coupled via a first interlock 780, the second delta
switching device 758 and the second wye switching device 752 are coupled
via a second interlock 782, and the third delta switching device 760 and
the third wye switching device 754 are coupled via a third interlock 784.
It should be noted that the interlocks 780, 782, and 784 may be the
mechanical interlocks described above. As such, only one of the first
delta switching device 756 and the first wye switching device 750 may be
closed at a time, only one of the second delta switching device 758 and
the second wye switching device 752 may be closed at a time, and only one
of the third delta switching device 760 and the third wye switching
device 754 may be closed at a time.

[0504] Additionally, as depicted, the output of first delta switching
device 756 and the output of first wye switching device 750 are
electrically coupled via a first interconnection 826. Similarly, the
output of the second delta switching device 758 and the output of second
wye switching device 752 are electrically coupled via a second
interconnection 832, and the output of the third delta switching device
760 and the output of the third wye switching device 754 are electrically
coupled via a third interconnection 820. Furthermore, the input of the
first wye switching device 750, the input of the second wye switching
device 752, and the input of the third wye switching device 754 are
electrically coupled via a fourth interconnection 831.

[0505] The steps in the wye two-step start and the phase sequential
wye-delta switching using nine switching devices are essentially the same
as using six switching devices. However, in the circuit diagram 748
depicted in FIG. 66 there are three mains line switching devices 762,
764, and 766 that are isolating the windings 774, 776, and 778. Thus,
before running the wye two-step start and the phase sequential wye-delta
switching, the control and monitoring circuitry 18 may send signals to
close the mains line switching devices 762, 764, and 766). After the
mains line switching devices are closed, the wye two-step start and the
phase sequential wye-delta switching may be executed the same as the
6-pole wye-delta starter.

[0506] More specifically, the control and monitoring circuitry 18 may
initiate the wye two-step start by closing the wye switching devices 754
and 752 simultaneously to connect windings 776 and 778 from line 770 to
line 772. Then, in the second step of the wye two-step start, the third
first wye switching device 750 may close in order to complete the wye
configuration and provide power to first winding 774.

[0507] Once the electric motor 24 is running in wye configuration and the
winding current waveforms have reached steady state, the phase sequential
switching to delta may initiate. Alternatively, the phase sequential
switching to delta may initiate any point after the motor is set in the
wye configuration. In some embodiment, the first step in the sequence may
include opening the wye switching devices 750. Thus, only windings 776
and 778 are connected and receiving power from line 770 to 772. Next, the
switching device 756 may be closed to connect first winding 774 in delta.
After switching device 756 closes, the motor is running in a mixed
wye-delta configuration with first winding 774 in delta and windings 776
and 778 in wye. Then, the remaining two closed wye switching devices 752
and 754 may be opened simultaneously and the electric motor 24 may be
single phasing (phase A) with only first winding 774 connected between
line 768 to line 770. As a result, the windings 774, 776, and 778 may
receive three-phase electric power from lines 768, 770, and 772, and the
electric motor 24 is running in a delta configuration.

[0508] In some embodiments, the 9-pole wye-delta starter 676 may be
implemented with single-pole, single current-carrying path switching
devices 218, as depicted in FIG. 67. More specifically, as depicted, the
first mains line 770 is electrically coupled to input terminal 788 of the
first mains line switching device 764, the second mains line 772 is
electrically coupled to input terminal 790 of the second mains line
switching device 766, and the third mains line 768 is electrically
coupled to input terminal 786 of the third mains line switching device
762. The output terminal 792 of the third mains line switching device 762
is electrically coupled to the input terminal 794 of the third delta
switching device 760, the output terminal 798 of the first mains line
switching device 764 is electrically coupled to the input terminal 800 of
the first delta switching device 756, and the output terminal 804 of the
second mains line switching device 766 is electrically coupled to the
input terminal 806 of the second delta switching device 758.

[0509] Additionally, the output terminal 824 of first delta switching
device 756 and the output terminal 828 of the first wye switching device
750 are electrically coupled by the first interconnect 828 (e.g., a first
bus bar). Similarly, the output terminal 830 of the second delta
switching device 758 and the output terminal 834 of the second wye
switching device 752 are electrically coupled by the second interconnect
832 (e.g., a second bus bar), and the output terminal 828 of the third
delta switching device 760 and the output terminal 822 of the third wye
switching device 754 are electrically coupled by the third interconnect
820 (e.g., a third bus bar). Furthermore, the input terminal 814 of the
first wye switching device 750, the input terminal 816 of the second wye
switching device 752, and the input terminal 810 of the third wye
switching device 754 are electrically coupled by the fourth interconnect
831 (e.g., a fourth bus bar).

[0510] Thus, the first winding 774 may be electrically coupled to either
output terminal 824, output terminal 828, or the first interconnect 826.
Additionally, the second winding 776 may be electrically coupled to
either output terminal 830, output terminal 834, or the second
interconnect 832. Furthermore, the third winding 704 may be electrically
coupled to either output terminal 818, output terminal 822, or the third
interconnect 826.

[0511] Additionally, as depicted, the first delta switching device 756 and
the first wye switching device 750 are mechanically coupled by the first
interlock 780. Similarly, the second delta switching device 758 and the
second wye switching device 752 are mechanically coupled by the second
interlock 782. Furthermore, the third delta switching device 760 and the
third wye switching device 754 are mechanically coupled by the third
interlock 784. It should be noted that the interlocks 780, 782, and 784
may each be the mechanical interlock described above.

[0512] An alternative embodiment of the 9-pole wye-delta starter 498 is
depicted in FIG. 68. In this embodiment, instead of utilizing three mains
line switching devices, this 9-pole wye-delta starter 498 utilizes three
additional delta switching devices. Thus, the 9-pole wye-delta starter
498 includes three wye switching devices 500, 502, and 504 and six delta
switching device 506, 508, 510, 512, 514, and 516. It should be noted
that the switching devices may be electromechanical single-pole, single
current-carrying path switching devices independently operated by the
control and monitoring circuitry 18. Additionally or alternatively, the
switching devices may include single-pole, multiple current-carrying path
switching devices. Independently operating the switching devices enables
making/breaking at different times and in different orders, among other
things. Further, the 9-pole wye-delta starter 498 may be enabled with or
without POW techniques. Similar to the previous embodiment of the 9-pole
wye-delta starter 748, the depicted embodiment of the 9-pole wye-delta
starter 498 isolates the motor windings 836, 838, and 840 from mains
lines 842, 844, and 846 by utilizing the three additional delta switching
devices 512, 514, and 516.

[0513] More specifically, the three mains lines 842, 844, and 846 supply
three-phase power and are electrically coupled to the six delta switching
devices 506, 508, 510, 512, 514, and 516. Three of the delta switching
devices 512, 514, and 516 are further electrically coupled to the motor
windings 836, 838, and 840, and the other three delta switching devices
506, 508, and 510 are further electrically coupled to the wye switching
devices 500, 502, and 504 as well as the three motor windings 836, 838,
and 840. Additionally, an advantage of utilizing the three additional
delta switching devices 512, 514, and 516 to isolate the electric motor
24, is that they may be utilized as disconnects in order to protect the
electric motor 24 from undesirable maintenance by faulty conditions or
the like. Furthermore, in some embodiments, delta switching devices 506,
508, 510, 512, 514, and 516 may be utilized to test for phase-to-ground
and phase-to-phase shorts before starting the motor.

[0514] In fact, the depicted embodiment may further improve detecting
phase-to-phase shorts by reducing duration electrical power is applied
during testing. More specifically, as depicted, when the first wye
switching device 500 is open, the first delta switching device 506 and a
first auxiliary delta switching device 512 are coupled in series with the
first winding 836. Similarly, when the second wye switching device 502 is
open, the second delta switching device 508 and a second auxiliary delta
switching device 514 are coupled in series with the second winding 838.
Furthermore, when the third wye switching device 504 is open, the third
delta switching device 510 and a third auxiliary delta switching device
516 are coupled in series with the third winding 840. Thus, the
opening/closing of each delta switching device and auxiliary delta
switching device may be offset from one another. In this manner, duration
the electric power is applied to the winding may be reduced even less
than the minimum duration either of the switching devices is closed.

[0515] Additionally, as depicted, the first delta switching device 506 and
the wye switching 500 are coupled via a first interlock 848, the second
delta switching device 508 and the second wye switching device 502 are
coupled via a second interlock 850, and the third delta switching device
510 and the third wye switching device 504 are coupled via a third
interlock 852. It should be noted that the interlocks 848, 850, and 852
may be the mechanical interlocks described above. As such, only one of
the first delta switching device 506 and the first wye switching device
500 may be closed at a time, only one of the second delta switching
device 508 and the second wye switching device 502 may be closed at a
time, and only one of the third delta switching device 510 and the third
wye switching device 504 may be closed at a time.

[0516] Similar to the previously described embodiment of the 9-pole
wye-delta starter 748, the output of first delta switching device 506 and
the output of first wye switching device 500 are electrically coupled via
a first interconnection 888. Similarly, the output of the second delta
switching device 508 and the output of second wye switching device 502
are electrically coupled via a second interconnection 894, and the output
of the third delta switching device 510 and the output of the third wye
switching device 504 are electrically coupled via a third interconnection
900. Furthermore, the input of the first wye switching device 500, the
input of the second wye switching device 502, and the input of the third
wye switching device 504 are electrically coupled via a fourth
interconnection 901.

[0517] Additionally, since the 9-pole wye-delta starter 498 include
auxiliary delta switching devices instead of mains switching devices, the
input of the first auxiliary delta switching device 512 and the third
delta switching device 510 are electrically coupled via a fifth
interconnection 862. Similarly, the input of the second auxiliary delta
switching device 514 and the input of the first delta switching device
506 are electrically coupled via a sixth interconnection 864.
Furthermore, the input of the third auxiliary switching device 516 and
the input of the second delta switching device 508 are electrically
coupled via a seventh interconnection 868.

[0518] The steps in the wye two-step start and the phase sequential
wye-delta switching using nine switching devices are essentially the same
as using six switching devices. However, in the depicted circuit diagram
498 there are three auxiliary delta switching devices (512, 514, and 516)
may isolate the windings (836, 838, and 840). Thus, before running the
wye two-step start and the phase sequential wye-delta switching, the
control and monitoring circuitry 18 may send signals to close the
auxiliary delta switching devices (512, 514, and 516). After the
auxiliary delta switching devices are closed, the wye two-step start and
the phase sequential wye-delta switching may be executed the same as the
6-pole wye-delta starter as discussed above with reference to the other
embodiment of the 9-pole wye-delta starter FIG. 66.

[0519] In some embodiments, the 9-pole wye-delta starter 498 may be
implemented with single-pole, single current-carrying path switching
devices 218, as depicted in FIG. 69. More specifically, the output
terminal 886 of first delta switching device 506 and the output terminal
884 of the first wye switching device 500 are electrically coupled by the
first interconnect 888 (e.g., a first bus bar). Similarly, the output
terminal 892 of the second delta switching device 508 and the output
terminal 890 of the second wye switching device 502 are electrically
coupled by the second interconnect 894 (e.g., a second bus bar).
Furthermore, and the output terminal 898 of the third delta switching
device 510 and the output terminal 896 of the third wye switching device
504 are electrically coupled by the third interconnect 900 (e.g., a third
bus bar). Furthermore, the input terminal 870 of the first wye switching
device 500, the input terminal 872 of the second wye switching device
502, and the input terminal 874 of the third wye switching device 504 are
electrically coupled by the fourth interconnect 901 (e.g., a fourth bus
bar).

[0520] Thus, the first winding 836 may be electrically coupled to either
output terminal 884, output terminal 886, or the first interconnect 888.
Additionally, the second winding 838 may be electrically coupled to
either output terminal 890, output terminal 892, or the second
interconnect 894. Furthermore, the third winding 840 may be electrically
coupled to either output terminal 896, output terminal 898, or the third
interconnect 900.

[0521] Additionally, as depicted, the input terminal 854 of the first
auxiliary delta switching device 512 and the input terminal of the third
delta switching device 512 are electrically coupled by the fifth
interconnection 862 (e.g., a fifth bus bar). Similarly, the input
terminal 856 of second auxiliary delta switching device 514 and the input
terminal of the first delta switching device 506 are electrically coupled
by the sixth interconnection 864 (e.g., a sixth bus bar). Furthermore,
the input terminal 858 of the third auxiliary delta switching device 516
and the input terminal 866 of the second delta switching device 508 are
electrically coupled by the seventh interconnection 868 (e.g., a seventh
bus bar).

[0522] Thus, the first mains line 842 may be electrically coupled to
either input terminal 854, input terminal 860, or the fifth
interconnection 862. Additionally, the second mains line 844 may be
electrically coupled to either input terminal 856, input terminal 858, or
the sixth interconnection 864. Furthermore, the third mains line 846 may
be electrically coupled to either input terminal 858, input terminal 866,
or seventh interconnection 868.

[0523] Furthermore, as depicted, the first delta switching device 506 and
the first wye switching device 500 are mechanically coupled by the first
interlock 848. Similarly, the second delta switching device 508 and the
second wye switching device 502 are mechanically coupled by the second
interlock 850. Furthermore, the third delta switching device 510 and the
third wye switching device 504 are mechanically coupled by the third
interlock 852. It should be noted that the interlocks 848, 850, and 852
may each be the mechanical interlock described above.

[0524] As evidenced by the varying configurations of a 9-pole wye-delta
starter, one of ordinary skill the art should appreciate that the
modularity provided be single pole, single current carrying path
switching device 218 enables varying advantages, such as adjusting
configuration based on size constraints. For example, one arrangement may
be desirable over the other depending on various factors (e.g., the
enclosure constraints, location of the electric motor 24, etc.), and
while either may achieve similar functions.

[0525] In addition to the wye-delta starters, other devices may also
utilize the techniques described herein, such as an electric motor
reverser, a two speed motor, or a motor drive bypass. To help illustrate,
one embodiment of an electric motor reverser 902, is shown in FIG. 70. As
depicted, the reverser 902 includes a first forward switching device 904,
a second forward switching device 906, a first reverse switching device
908, a second reverse switching device 910, and a common switching device
912. More specifically, as depicted, the input of the first forward
switching device 904 and the input of the second reverse switching device
910 are electrically coupled by a first interconnect 934. Similarly, the
input of the first reverse switching device 908 and the input of the
second forward switching device 906 are electrically coupled by a second
interconnect 940. Furthermore, the output of the first forward switching
device 904 and the output of the first reverse switching device 908 are
electrically coupled by a third interconnect 946. Similarly, the output
of the second reverse switching device 910 and the output of the second
forward switching device 906 are electrically coupled by a fourth
interconnect 952.

[0526] Additionally, as depicted, the first forward switching device 904
and the first reverse switching device 908 are coupled via a first
interlock 914, and the second forward switching device 906 and the second
reverse switching device 910 are coupled via a second interlock 916. In
other words, only one of the first forward switching device 904 and the
first reverse switching device 908 may be closed at a time. Similarly,
only one of the second forward switching device 906 and the second
reverse switching device 910 may be closed at a time. Additionally,
operation of the reverser 902 may generally be controlled by the control
and monitoring circuitry 18.

[0527] In the depicted embodiment, when the first forward switching device
904 is closed, a first phase of electric power (e.g., phase A) is
connected from the first mains line 918 to the first motor terminal 920
of the electric motor 24; when the second forward switching device 906 is
closed, a second phase of electric power (e.g., phase B) is connected
from the second mains line 922 to the second motor terminal 924 of the
electric motor 24; and when the common switching device 912 is closed, a
third phase of electric power (e.g., phase C) is connected from the third
mains line 926 to the third motor terminal 928 of the electric motor 24.
Thus, when the first forward switching device 904, the second forward
switching device 906, and the common switching device 912 are closed, the
motor rotates in a forward direction (e.g., first direction).

[0528] Generally, a reverser may change the rotational direction of an
electric motor 24 (e.g., from forward to reverse) by disconnected
electric power and reconnecting the electric power with two of the phases
switched. Accordingly, in some embodiments, to reverse the electric
motor, the control and monitoring circuitry 18 may break the first
forward switching device 904, the second forward switching device 906,
and the common switching device 912. For example, the second forward
switching device 906 may be opened based upon a first current
zero-crossing, and the first forward switching device 904 and the common
switching device 912 may be opened based upon a subsequent zero-crossing.
Additionally or alternatively, POW techniques are not used and the
switching devices may be opened after a brief delay.

[0529] Then, the first reverse switching device 908, second reverse
switching device 910, and the common switching device 912 may be closed.
For example, the second reverse switching device 910 and the common
switching device 912 may be closed based upon a first predicted current
zero-crossing (e.g., maximum line-to-line voltage), and the first reverse
switching device 908 may be closed based upon a subsequent predicted
current zero-crossing. More specifically, when the first reverse
switching device 908 is closed, the second phase of electric power (e.g.,
phase B) is connected from the second mains line 922 to the first motor
terminal 920; when the second reverse switching device 910 is closed, the
first phase of electric power (e.g., phase A) is connected from the first
mains line 918 to the second motor terminal 924, and when the common
switching device 912 is closed, the third phase of electric power (e.g.,
phase C) is connected from the third mains line 926 to the third motor
terminal 928. Thus, when the first reverse switching device 908, the
second reverse switching device 910, and the common switching device 912
are closed, the motor rotates in the reverse direction (e.g., opposite
direction).

[0530] In some embodiments, since the common switching device 912 simply
disconnects and reconnects the same phase of electric power (e.g., phase
C) to the same motor terminal (e.g., third motor terminal) of the
electric motor, the common switching device 912 may remain closed during
the reverse operation. In such embodiments, even though the common
switching device 912 remains closed, the common switching device 912 may
still be included to disconnect the third phase of electric power from
the electric motor 24. Additionally or alternatively, in other
embodiments, the common switching device 912 may be removed entirely.

[0531] In either embodiment where the one phase of electric power remains
connected during the reverse operation, the control and monitoring
circuitry 18 may break the first forward switching device 904 and the
second forward switching device 906. For example, the second forward
switching device 906 may be opened based upon a first current
zero-crossing and the first forward switching device 904 may be opened
based upon a subsequent current zero-crossing. Then the control and
monitoring circuitry may make the first reverse switching device 908 and
the second reverse switching device 910. For example, the second
switching device 910 may be closed based upon a first predicted current
zero-crossing and the first reverse switching device 908 may be closed
based upon a subsequent predicted current zero-crossing.

[0532] In some of the embodiments of the reverser 902 described above,
each switching device may be controlled independently. For example, as
described above, the first forward switching device 904 and the second
forward switching device 906 may make/break at different times and in
different orders. Accordingly, to improve the control over each switching
device, the reverser 902 may be implemented with single-pole switching
devices (e.g., single-pole, single current-carrying path switching
devices 218), as depicted in FIG. 71.

[0533] To implement the reverser 902, as depicted, the input terminal 930
of the first forward switching device 904 and the input terminal 932 of
the second reverse switching device 910 are electrically coupled via the
first interconnection 934 (e.g., a first bus bar). Thus, the first mains
line 918 may be connected to either input terminal 930, input terminal
932, or the first interconnection 934. Additionally, as depicted, the
input terminal 936 of the first reverse switching device 908 and the
input terminal 938 of the second forward switching device 906 are
electrically coupled via the second interconnection 940 (e.g., a second
bus bar). Thus, the second mains line 922 may be connected to either
input terminal 936 or 938.

[0534] On the output side, the output terminal 942 of the first forward
switching device 904 and the output terminal 944 of the first reverse
switching device 908 are electrically coupled via the third interconnect
946 (e.g., a third bus bar). Thus, the first motor terminal 920 may be
connected to either output terminal 942, output terminal 944, or the
third interconnect 946. Additionally, as depicted, the output terminal
948 of the second reverse switching device 910 and the output terminal
950 of the second forward switching device 906 are electrically coupled
via the fourth interconnect 952 (e.g., a fourth bus bar). Thus, the
second motor terminal 924 may be connected to either output terminal 948,
output terminal 950, or the fourth interconnect 952.

[0535] Furthermore, in the depicted embodiment, the input terminal 954 of
the common switching device 912 may be connected to the third mains line
926 and the output terminal 956 of the common switching device 912 may be
connected to the third motor terminal 928. As described above, the
reverser 902 may be implemented with or without the common switching
device 912. Thus, the modular nature of the single-pole path switching
devices 218 (e.g., single-pole, single current-carrying path switching
devices) enables each implementation to be individually configured. For
example, in a first configuration, the reverser 902 may include the
common switching device 912, but in a second configuration, the reverser
902 may exclude the common switching device 912. Even though the common
switching device 912 is excluded in the second configuration, the
configuration of the remaining switching devices (e.g., 904-910) will
largely remain the same.

[0536] Similar to the motor reverser 902, a two speed motor may be
implemented using five single pole, single current carrying path
switching devices 218. As described above, a motor drive bypass may also
utilize the techniques described herein. To help illustrate, one
embodiment of a motor drive bypass 958 that may be utilized to bypass the
motor drive 960, is shown in FIG. 72. In some embodiments, the motor
drive 960 may be a soft starter, across the line starter, variable
frequency drive, or the like.

[0537] As depicted, the motor drive bypass 958 includes a first mains
disconnect 962, a second mains disconnect 964, a third mains disconnect
966, a first input disconnect 968, a second input disconnect 970, a third
input disconnect 972, a first bypass switching device 974, a second
bypass switching device 976, a third bypass switching device 978, a first
output disconnect 980, a second output disconnect 982, and a third output
disconnect 984 (e.g., switching devices). More specifically, the output
of the first mains disconnect 962, the input of the first input
disconnect 968, and the input of the first bypass switching device 974
are electrically coupled by a first interconnect 986. Similarly, the
output of the second mains disconnect 964, the input of the second input
disconnect 970, and the input of the second bypass switching device 976
are electrically coupled by a second interconnect 996. Furthermore, the
output of the third mains disconnect 926, the input of the third input
disconnect 972, and the input of the third bypass switching device 978
are electrically coupled by a third interconnect 1006.

[0538] Additionally, as depicted, the output of the first bypass switching
device 974 and the output of the first output disconnect 980 are
electrically coupled by a fourth interconnect 992. Similarly, the output
of the second bypass switching device 976 and the output of the second
output disconnect 982 are electrically coupled by a fifth interconnect
1002. Furthermore, the output of the third bypass switching device 978
and the output of the third output disconnect 984 are electrically
coupled by a sixth interconnect 1012.

[0539] Operation of the motor drive bypass 958 may generally be controlled
by the control and monitoring circuitry 18. Generally, when the
disconnects are closed and the bypass switching devices 974-978 are open,
the motor drive 960 receives three-phase electric power and outputs
three-phase electric power. For example, in the depicted embodiment, the
r input of the motor drive 960 receives a first phase of electric power
(e.g., phase A) from the first mains line 918, the s input of the motor
drive 960 receives a second phase of electric power (e.g., phase B) from
the second mains line 922, and the t input of the motor drive 960
receives a third phase of electric power (e.g., phase C) from the third
mains line 926. Additionally, the u output of the motor drive 960 outputs
the first phase of electric power to the first motor terminal 920, the v
output of the motor drive 960 outputs the second phase of electric power
to the second motor terminal 924, and the w output of the motor drive 960
outputs the third phase of electric power to the third motor terminal
928. It should be noted that other motor or load controlling devices may
be used.

[0540] Accordingly, control and monitoring circuitry 18 may utilize the
mains disconnects 962-966 to selectively connect and disconnect electric
power from both the motor driver 960 and the electric motor 24. More
specifically, when the first mains disconnect 962 is opened, the first
phase of electric power is disconnected; when the second mains disconnect
964 is opened, the second phase of electric power is disconnected; and
when the third mains disconnect 966 is opened, the third phase of
electric power is disconnected. For example, the second mains disconnect
964 may be opened based upon a first current zero-crossing, and the first
mains disconnect 962 and the third mains disconnect 966 may be opened
based upon a subsequent current zero-crossing. However, in some
embodiments, POW techniques may not be used and the switching devices may
be closed and opened in any desired manner. In some embodiments, the
mains disconnects 962-966 may be optionally excluded because the electric
power may be selectively connected and disconnected from both the motor
drive 960 and the electric motor 24, for example, by the input
disconnects 966-970.

[0541] Instead of completely disconnecting electric power to the electric
motor 24, at times, it may be desirable to disconnect electric power from
the motor drive 960 but continue supplying power to the electric motor
24, for example, to reduce power consumption or to perform maintenance on
the motor drive 960. Accordingly, the bypass switching devices 974-978
may be closed to bypass the motor drive 960.

[0542] More specifically, control and monitoring circuitry 18 may open the
input disconnects 968-972 and the output disconnects 980-984 to
disconnect electric power from the motor drive 960. In some embodiments,
the input disconnects 968-972 may be opened substantially simultaneously.
In other embodiments, the input disconnects 968-972 may be opened using
point-on-wave (POW) techniques. For example, the second input disconnect
970 may be opened based upon a first current zero-crossing, and the first
input disconnect 968 and the third input disconnect 972 may be opened
based upon a subsequent current zero-crossing. Similarly, in some
embodiments, the output disconnects 980-984 may be opened substantially
simultaneously. In other embodiments, the output disconnects 980-984 may
be opened using POW techniques. For example, the second output disconnect
982 may be opened based upon a first current zero-crossing, and the first
output disconnect 980 and the third output disconnect 984 may be opened
based upon a subsequent current zero-crossing.

[0543] To reduce the possibility of electric power being back fed into the
motor drive 960 via the outputs, the bypass switching devices 974-978 may
be closed after the output disconnects 980-984 are opened. In some
embodiments, the bypass switching devices 974-978 may be closed
substantially simultaneously. In other embodiments, the bypass switching
devices 974-978 may be closed using POW techniques. For example, the
first bypass switching device 974 and the third bypass switching device
978 may close based upon a first predicted current zero-crossing, and the
second bypass switching device 976 may close based upon a subsequent
predicted current zero-crossing.

[0544] Once the bypass switching device 974-978 make, the first phase of
electric power may be supplied from the first mains lines 918 through the
first bypass switching device 974 to the first motor terminal 920, the
second phase of electric power may be supplied from the second mains
lines 922 through the second bypass switching device 976 to the second
motor terminal 924, and the third phase of electric power may be supplied
from the third mains line 926 through the third bypass switching device
978 to the third motor terminal 928. In other words, the drive bypass 958
enables the electric motor 24 to continue actuating even after the motor
drive 960 is bypassed. This may prove especially useful for high
reliability systems, such as a waste management system.

[0545] In some of the embodiments of the drive bypass 958 described above,
each switching device may be controlled independently. For example, as
described above, the first bypass switching device 974 and the second
bypass switching device 976 may make/break at different times and in
different orders. Accordingly, to improve the control over each switching
device, the drive bypass 958 may be implemented with single-pole
switching devices 218 (e.g., single-pole, single current-carrying path
switching devices), as depicted in FIG. 73.

[0546] To implement the drive bypass 958, as depicted, the output terminal
of the first mains disconnect 962 is electrically coupled to the input
terminal of the first input disconnect 968 and the input terminal of the
first bypass switching device 974 via the first interconnect 986 (e.g., a
first bus bar). Thus, the first mains line 918 may be connected to the
input terminal 988 of the first mains disconnect 962 and the output
terminal 990 of the first input disconnect 968 may be connected to the r
input of the motor drive 960.

[0547] Similarly, as depicted, the output terminal of the second mains
disconnect 964 is electrically coupled to the input terminal of the
second input disconnect 970 and the input terminal of the second bypass
switching device 976 via the second interconnect (e.g., a second bus
bar). Thus, the second mains line 922 may be connected to the input
terminal 998 of the second mains disconnect 964 and the output terminal
1000 of the second input disconnect 970 may be connected to the s input
of the motor drive 960.

[0548] Furthermore, as depicted, the output terminal of the third mains
disconnect 966 is electrically coupled to the input terminal of the third
input disconnect 972 and the input terminal of the third bypass switching
device 978 via the third interconnect 1006 (e.g., a third bus bar). Thus,
the third mains line 926 may be connected to the input terminal 1008 of
the third mains disconnect 966 and the output terminal 1010 of the third
input disconnect 970 may be connected to the t input of the motor drive
960.

[0549] As depicted, the output terminal of the first output disconnect 980
and the output terminal of the first bypass switching device 974 are
electrically coupled by the fourth interconnect 992 (e.g., a fourth bus
bar). Similarly, the output terminal of the second output disconnect 982
and the output terminal of the second bypass switching device 974 are
electrically coupled by the fifth interconnect 1002 (e.g., a fifth bus
bar). Additionally, the output terminal of the third output disconnect
984 and the output terminal of the third bypass switching device 978 are
electrically coupled by the sixth interconnect 1012 (e.g., a sixth bus
bar).

[0550] Thus, the input terminal 994 of the first output disconnect 980 may
be connected to the u output of the motor drive 960, the input terminal
1004 of the second output disconnect 982, may be connected to the v
output of the motor drive 960, and the input terminal 1014 of the third
output disconnect 984 may be connected to the w output of the motor drive
960. Moreover, the first motor terminal 920 may be electrically coupled
to the output terminal of the first output disconnect 980, the output
terminal of the first bypass switching device 974, or the fourth
interconnect 992. Similarly, the second motor terminal 924 may be
electrically coupled to the output terminal of the second output
disconnect 982, the output terminal of the second bypass switching device
976, or the fifth interconnect 1002. Furthermore, the third motor
terminal 928 may be electrically coupled to the output terminal of the
third output disconnect 984, the output terminal of the third bypass
switching device 978, or the sixth interconnect 1012.

[0551] Additionally, as described above, the drive bypass 958 may be
implemented with or without the main line disconnects 962-966. Thus, the
modular nature of the single-pole switching devices 218 (e.g.,
single-pole, single current-carrying path switching devices) enables each
implementation to be individually configured. For example, in a first
configuration, the drive bypass 958 may include the main line disconnects
962-966, but in a second configuration, the drive bypass 958 may exclude
the main line disconnects 962-966. In fact, in some embodiments,
excluding the main line disconnects 962-966 may enable the bypass
switching devices 974-978 and the output disconnects 980-984 to be
adjacent with a mechanical interlock placed therebetween. Moreover, by
adjusting the size and length of the bus bars may enable the placement of
each switching device 218 to be individually determined.

[0552] Starting with FIG. 74, the single-pole switching devices 1014,
1016, and 1018 may function as a three pole contactor using direct on
line (DOL) operation to connect and disconnect three phase power from the
power source 12 to the load 14. It should be appreciated that the
configuration depicted in FIG. 74 may function as a three pole contactor
using DOL with or without POW techniques. As described above, various
benefits may be achieved using POW techniques, such as reducing inrush
current when closing and inhibiting arcing when opening.

[0553] In some embodiments, each of the single-pole switching devices
1014, 1016, and 1018 may be independently controllable and can be
operated in any desired sequence. For example, each single-pole switching
device may be opened/closed at the same time. In another example, two of
the single-pole switching devices 1014 and 1016 may be opened/closed at a
first time and a third single-pole switching device 1018 may be closed at
a second time after the first time. In yet another example, one of the
single-pole switching devices 1014 may be opened/closed at first time and
then the other two single-pole switching devices 1016 and 1018 may be
closed at a second time after the first time.

[0554] To this end, using single-pole switching devices enables taking
turns between the order with which the single-pole switching devices are
opened/closed to enable reducing wear and tear on the switching devices.
For example, the single-pole switching device that breaks first during
one operation may be controlled to break last in a subsequent operation.
Indeed, certain schemes may be used, such as round robin, when selecting
the order in which to break and/or make the single-pole switching
devices.

[0555] FIG. 75 depicts the three single-pole switching devices 1014, 1016,
and 1018 with an added fourth single-pole switching device 1020 used as a
neutral or ground. The single-pole switching devices 1014, 1016, 1018,
and 1020 may supply power from the power source 12 to the load 14.
Essentially, in some embodiments, the depicted configuration may be
operated in the same way as the configuration in FIG. 74 as a standard
three pole contactor using DOL operation with or without POW techniques
but accounting for the fourth single-pole switching device 1020 to
connect and disconnect to ground as desired. Additionally, in some
embodiments, the four single-pole switching devices 1014, 1016, 1018, and
1020 may be independently controlled to connect and disconnect in any
sequence to function as a soft starter for a motor (e.g., using
wye-delta) with or without POW techniques, as described above.

[0556] The modular configurations of single-pole switching devices
described above may be achieved through various connection arrangements
as shown in FIGS. 76-80. As may be appreciated, the design of the power
terminals on the single-pole switching devices may be modified as desired
to enable the switching devices to be connected in multiple ways that may
reduce wiring complexity and configuration size.

[0557] For example, FIG. 76 illustrates two identical single-pole
switching devices 1022 and 1024 arranged next to one another. The
single-pole switching device 1022 and 1024 each includes two power
terminals located at the same height protruding from two opposite sides
of the switching devices 1022 and 1024. That is, the single-pole
switching device 1022 includes a first power terminal 1026 and a second
power terminal 1028 at the same height and the single-pole switching
device 1024 includes a first power terminal 1030 and a second power
terminal 1032 at the same height. As depicted, the second power terminal
1028 of the single-pole switching device 1022 is aligned with the first
power terminal 1030 of the single-pole switching device 1024. The power
terminals 1028 and 1030 may be connected using a bus bar 1034 with
connecting pins 1036 that are inserted through apertures 1038 in the bus
bar 1034 and the power terminals 1028 and 1030.

[0558] In another embodiment, the power terminals of the single-pole
switching devices may be located at different heights on the two opposing
sides, as shown in FIG. 77. As illustrated, a single-pole switching
device 1040 includes a first power terminal 1042 located at a lower
height on one side than a second power terminal 1044 on an opposing side
of the single-pole switching device 1040. Using an identical single-pole
switching device 1046 with power terminals located at the same heights,
the two switching devices 1040 and 1046 may be connected by overlapping
the power terminals. As shown, a first power terminal 1048 of the
single-pole switching device 1046 aligns underneath the second power
terminal 1044 of the single-pole switching device 1040, and the power
terminals 1044 and 1048 are connected via a connecting pin 1036. As such,
the depicted configuration may obviate use of a bus bar to connect the
single-pole switching devices 1040 and 1046.

[0559] In another embodiment, the power terminals of the single-pole
switching devices may be configured to fit together, as shown in FIG. 78.
As illustrated, a single-pole switching device 1050 includes a first
power terminal 1052 with a groove on the bottom of the terminal on one
side and a second power terminal 1054 with a groove on the top of the
terminal that matches the groove of the first power terminal 1052 on the
opposing side. Using an identical single-pole switching device 1056 with
power terminals including the grooves, the two switching devices 1050 and
1056 may be connected by mating the power terminals together. As shown, a
first power terminal 1058 of the single-pole switching device 1056 fits
with the second power terminal 1054 of the single-pole switching device
1050 by mating grooves, and the power terminals 1054 and 1058 are
connected via a single connecting pin 1036. As such, the depicted
configuration may obviate use of a bus bar to connect the single-pole
switching devices 1050 and 1056.

[0560] FIGS. 79 and 80 depict top views of various configurations of more
than two single-pole switching devices that reduce the amount of wiring
needed to connect the switching devices. For example, FIG. 79 illustrates
single-pole switching devices 1060, 1062, and 1064 that include power
terminals at varying heights so the power terminals may overlap one
another. That is, power terminal 1066 of switching device 1060 is
highest, power terminal 1068 of switching device 1062 is at an
intermediate height, and power terminal 1070 is at a lowest height.
Accordingly, the power terminals may be stacked on top of one another and
connected via a single connecting pin 1036. As may be appreciated,
single-pole switching devices may be arranged to fit within the physical
constraints of certain housings and may do so by reducing wiring through
direct connections via power terminals with a single connector pin 1036.

[0561] Additionally, FIG. 80 illustrates single-pole switching devices
1072, 1074, and 1076 that include power terminals 1078, 1080, and 1082
located at the same heights. As described above, a bus bar may be used to
connect power terminals that do not overlap. For example, in the depicted
embodiment, the three power terminals 1078, 1080, and 1082 are connected
via a "T" bus bar 1084 that aligns with apertures 1038 and secured with
connecting pins 1036. Using the above configurations to connect the
single-pole switching devices may provide the benefit of reducing wiring
complexity when arranging certain motor starters.

Provided System Improvements

[0562] Moreover, the techniques described herein may facilitate improved
operation of one or more components in the system 10. In some
embodiments, sniffing techniques may be used to facilitate controlling
temperature of a load 14, particularly when the load 14 is not in
operation. For example, control circuitry 18 may instruct single pole
switching devices (e.g., 576, 578, or 580) to periodically conduct
current through windings in an electric motor 24, thereby heating the
windings. In some embodiments, heating the windings may facilitate
subsequent startup of the motor 24, particularly in cold environments.

[0563] To help illustrate, one embodiment of a process 1100 for
maintaining temperature in an electric motor is described in FIG. 81.
Generally, process 1100 includes ceasing operation of a load (process
block 1102) and determining whether desirable to heat the load (decision
block 1104). When desirable to heat the load, the process 1100 further
includes supplying a first phase and a second phase of electric power
(process block 1106), supplying the first phase and a third phase of
electric power (process block 1108), and supplying the second phase and
the third phase of electric power (process block 1110). The process 1100
may be implemented via computer-readable instructions stored in a
non-transitory article of manufacture (e.g., the memory 226, 20, 46
and/or other memories) and executed via processor 224, 19, 45 and/or
other control circuitry.

[0564] Accordingly, control circuitry 18 may instruct an electric motor 24
to cease operation (process block 1102). In some embodiments, the control
circuitry 18 may cease operation of the electric motor 24 by instructing
one or more switching devices (e.g., single pole switching devices 576,
578, and 580) to open, thereby disconnecting electric power from the
motor 24.

[0565] The control circuitry 18 may then determine whether it is desirable
to heat the electric motor 24 (decision block 1104). In some embodiments,
the control circuitry 18 may determine temperature of the electric motor
24 via a temperature sensor. In such embodiments, the control circuitry
18 may determine that it is desirable to heat the electric motor 24 when
the temperature of the motor 24 reaches a threshold. Additionally or
alternatively, the control circuitry 18 may periodically determine that
it is desirable to heat the electric motor, for example, based on a
timer.

[0566] When not desirable to heat the electric motor, control circuitry 18
may continue waiting until heating is desired (arrow 1112). In some
embodiments, the control circuitry 18 may periodically poll the
temperature sensors to determine whether temperature has reached the
threshold.

[0567] On the other hand, when heating is desirable, the control circuitry
18 may instruct the one or more switching devices to connect a first
phase (e.g., phase A) and a second phase (e.g., phase B) of electric
power to a first winding in the motor 24 for the short duration (process
block 1106). For example, in some embodiments the control circuitry 18
may instruct the first single pole switching device 576 and the second
single pole switching device 578 to close for a short duration (e.g.,
sniff) at a first time. In this manner, the first winding may be heated
due to conduction of current.

[0568] Additionally, the control circuitry 18 may instruct the one or more
switching devices to connect the first phase (e.g., phase A) and a third
phase (e.g., phase C) of electric power to a second winding in the motor
24 for the short duration (process block 1108). For example, in some
embodiments, the control circuitry 18 may instruct the first single pole
switching device 576 and the third single pole switching device 580 to
close for a short duration (e.g., sniff) at a second time. In this
manner, the second winding may be heated due to conduction of current.

[0569] Furthermore, the control circuitry 18 may instruct the one or more
switching devices to connect the second phase (e.g., phase B) and the
third phase (e.g., phase C) of electric power to a third winding in the
motor 24 for the short duration (process block 1110). For example, in
some embodiments, the control circuitry 18 may instruct the second single
pole switching device 578 and the third single pole switching device 580
to close for a short duration (e.g., sniff) at a third time. In this
manner, the third winding may be heated due to conduction of current.

[0570] As described above, supplying two phases of electric power when the
motor 24 is stationary may be insufficient to begin rotation of the motor
24. As such, the heating of the windings may be performed while
maintaining the motor 24 stationary (e.g., non-operational).
Additionally, in some embodiments, heating of the electric motor 24 may
be coordinated with testing for phase-to-ground faults and/or
phase-to-phase faults. Accordingly, the control circuitry 18 may instruct
each pair of the single pole switching device 576, 578, and 580 to close
based at least in part on a predicted current-zero crossing, thereby
reducing impact of any potential faults.

[0571] Moreover, even when the load 14 is in operation (e.g., electric
motor 24 is rotating), the temperature of the load 14 may be controlled
to improve operation. For example, when an electric motor 24 is connected
in a partial wye, a partial delta, or a mixed wye-delta configuration,
the electric power supplied to each of the windings may vary. As such,
the temperature of each winding may differ based at least in part on the
amount of conducted electric power. Thus, to facilitate maintaining
approximately equal temperature between the windings, a wye-delta starter
may periodically rotate which windings are connected in what
configuration, particularly remaining in a configuration for an extended
period.

[0572] For example, in a configuration where the wye-delta starter only
connects one winding in a delta configuration (e.g., a partial delta
configuration described in FIG. G), the wye-delta starter may
periodically change which winding is connected in the delta
configuration. More specifically, the wye-delta starter may periodically
rotate between connecting the first winding 386 in the delta
configuration, connecting the second winding 388 in the delta
configuration, and connecting the third winding 390 in the delta
configuration. In this manner, by connecting each winding for
approximately the same duration in the delta configuration, the
temperature of the windings may be maintained approximately equal. One of
ordinary skill should appreciate that such a rotation between the
windings may also be applicable to other partial delta configuration,
partial wye configurations, and mixed wye delta configurations.

[0573] In addition to improving operation of a load 14, the techniques
described herein may also facilitate improving operation of the switching
devices. More specifically, oxidation may build up on contactor pads of
the switching devices due to contactor contamination or environmental
conditions, such as dust. Accordingly, controlled arcing may be used to
clean the contactor pads by burning off oxidation, thereby improving
performance and/or lifespan of the switching device.

[0574] To help illustrate, one embodiment of a process 1114 for cleaning
contactor pads of a switching device is described in FIG. 82. Generally,
the process 1114 includes making a switching device (process block 1116)
and determining when desirable to break the switching device (decision
block 1118). When desired to break the switching device, the process
includes determine whether desirable to clean the switching device
(decision block 1120), breaking based on a current zero-crossing when not
desirable to clean the switching device (process block 1122), and
creating an arc when breaking when desirable to clean the switching
device (process block 1124). The process 1114 may be implemented via
computer-readable instructions stored in a non-transitory article of
manufacture (e.g., the memory 226, 20, 46 and/or other memories) and
executed via processor 224, 19, 45 and/or other control circuitry.

[0575] Accordingly, control circuitry 18 may instruct a switching device
to make, thereby connecting electric power to a load 14 (process block
1116). The control circuitry 18 may then determine whether it is
desirable to break the switching device (process block 1118). In some
embodiments, the control circuitry 18 may determine that it is desirable
to break when desirable to disconnect electric power from the load 14. If
not desirable to break, the control circuitry 18 may instruct the
switching device to remain closed and wait until desirable to break
(arrow 1126).

[0576] On the other hand, when desirable to break, the control circuitry
18 may determine whether it is desirable to clean the switching device
(decision block 1120). In some embodiments, the control circuitry 18 may
determine that is desirable to clean the switching device after a set
number of breaks, for example, every twentieth break. Additionally or
alternatively, the control circuitry 18 may determine that it is
desirable to clean based on duration the switching device has been in
operation and/or duration the switching device has been closed.

[0577] When not desirable to clean, the control circuitry 18 may instruct
the switching device to break based at least in part on a current
zero-crossing of the conducted electric power (process block 1122). In
some embodiments, the control circuitry 18 may instruct the switching
device to break slightly before or at the current zero-crossing, thereby
reducing the likelihood and/or magnitude of any arcing. As described
above, it may be desirable to miss the mark short of the current
zero-crossing and open when the current is going downward on a half cycle
to the current zero-cross, as opposed to missing the mark after the
current zero-crossing.

[0578] On the other when desirable to clean, the control circuitry 18 may
instruct the switching device to break such that an arc is created as the
contactor pads open (process block 1124). In this manner, the heat
produced by the arcing may burn off any oxidation on the contactor pads,
thereby cleaning the switching device. As described above, the magnitude
of arcing may be directly based on where on the current waveform the
switching device breaks. More specifically, the farther the break is from
a subsequent current zero-crossing the larger the magnitude of produced
arcing. As such, in some embodiments, the control circuitry 18 may
determine when to break based on a desired amount of arcing. For example,
when the switching device has not been cleaned for a longer duration, the
control circuitry 18 may determine that greater amount of cleaning is
desirable and break farther from the subsequent current-zero crossing.

[0579] Additionally, in some instances, arcing may cause atoms from one
contactor pad to transfer to the other contactor pad. Thus, in some
embodiments, the control circuitry 18 may also determine when to break
the switching device based on direction desirable to transfer atoms. In
fact, in some embodiments, the control system 18 may break the switching
device such that the contact pads take turns being the anode and the
cathode. In this manner, it may be possible to retain relatively even
number of atoms on each contactor pad.

[0580] 74 illustrates an embodiment where three single-pole switching
devices 1014, 1016, and 1018 are used to connect and disconnect three
phase power and FIG. 75 illustrates an embodiment where four single-pole
switching devices 1014, 1016, 1018, and 1020 are used to connect and
disconnect three phase power plus a neural (e.g., ground).

[0581] While only certain features of the disclosure have been illustrated
and described herein, many modifications and changes will occur to those
skilled in the art. It is, therefore, to be understood that the appended
claims are intended to cover all such modifications and changes as fall
within the true spirit of the disclosure.